Debt Consolidation Remortgage: Calculator and Methodology

The Apparent Saving vs The Real Cost

Debt consolidation looks attractive because two numbers drop: the headline interest rate (from 20%+ on credit cards to 4-5% on mortgage) and the monthly payment (from aggressive repayment schedules to a 20-year amortisation). Over a 2-year horizon, consolidation typically saves money. Over a 15-20 year horizon, it usually costs more in total interest because of the much longer repayment period.

Example: £15,000 credit card debt at 21.9% APR paid over 3 years at £575/month. Total interest paid: £5,700. Same £15,000 added to a £200,000 mortgage at 4.30% over 20 years. Monthly impact: roughly £93. Total interest attributable to the £15,000 over 20 years: £7,340. The mortgage approach costs £1,640 more in interest but frees up £482/month of cash flow — whether that is a good trade depends on what the cash flow is used for.

Debt type	Typical APR	Typical term if unconsolidated	Total interest if consolidated into 20y mortgage
Credit card (£8,000)	21.9%	3-4 years	£3,920
Store card (£2,500)	29.9%	2 years	£1,225
Personal loan (£12,000)	9.5%	5 years	£5,870
Car finance (£18,000)	11.9%	4 years	£8,800

The Secured Debt Risk

The biggest difference between unsecured debt and a consolidated mortgage is not cost — it is security. Credit card debt and personal loans are unsecured; the lender can sue you, register a CCJ, or appoint a debt collector, but they cannot take your home without a separate charging order. Mortgage debt is secured on the property from day one; miss payments and repossession is the ultimate sanction.

The FCA requires mortgage advisers to clearly explain this security transfer under MCOB rules and Consumer Duty. A responsible adviser will walk through the worst case: you lose your job, miss 3 months of payments, the lender issues a possession order. Under the unsecured structure you would face unpaid debts but a roof over your head; under consolidation you could lose the house.

Not every consolidation is wrong. For borrowers with stable employment, low unsecured debt relative to equity, and a clear plan to repay the consolidated amount via overpayments within 3 to 5 years, consolidation can be appropriate. For borrowers in income distress or with high variable income, spreading debt onto the house is usually the wrong call.

Worked Example 1: The Reasonable Case

Emily has £18,000 of unsecured debt: £10,000 credit cards at 21.9% APR, £8,000 personal loan at 9.5% APR. Her current monthly payments total £620. She has stable employment (£58,000 salary, public sector), a £200,000 mortgage balance with £85,000 equity in a £285,000 property, and 22 years remaining at 4.30%. Current mortgage payment £1,180.

Consolidation: add £18,000 to the mortgage (new balance £218,000, new LTV 76.5% — still within 80% tier). New monthly payment £1,286 (+£106). Total monthly saving vs unsecured: £620 − £106 = £514 per month of released cash flow.

Total cost analysis: if Emily uses the freed £514/month to overpay the mortgage, she can clear the additional £18,000 in about 33 months. Total interest on the consolidated debt: roughly £1,900. Compared to £5,400 of interest on the unsecured at their natural pace, consolidation plus disciplined overpayment saves £3,500. This works because Emily commits to overpaying.

Worked Example 2: The Cautionary Case

James has £24,000 of unsecured debt: £9,000 credit cards, £5,000 store cards, £10,000 car finance. Monthly payments total £780. He is self-employed, income averaging £42,000 but varying ±30% year-to-year. Mortgage balance £178,000, property £240,000, 25 years remaining at 4.50%.

Consolidation: add £24,000, new balance £202,000, new LTV 84.2% — pushes him into 85% tier (rate 4.75%). Old payment £978, new payment £1,150 (+£172). Monthly cash flow improvement £780 − £172 = £608. Sounds great.

Over 25 years at 4.75%, total interest on the £24,000 is approximately £18,500, compared to roughly £7,200 if unsecured debts were paid at their natural schedule. Consolidation costs James an extra £11,300 in interest over the full term. If his income drops in a bad year and he cannot overpay, the consolidation compounds into a very expensive loan. Plus, if he fails to change behaviour, he may run up the credit cards again, doubling the problem. For James, the FCA's suitability rules would usually point to a debt management plan or IVA rather than consolidation.

Worked Example 3: Using a Secured Loan Instead

Priya has £14,000 unsecured debt (£9,000 credit cards, £5,000 personal loan). Her current mortgage is a 2-year fixed at 1.99% with 4 years remaining and a 3% ERC. Remortgaging to consolidate would trigger a £5,400 ERC on her £180,000 balance. She cannot take further borrowing from her current lender beyond modest limits.

Option A: stay on mortgage, take a secured loan of £14,000 at 8.9% over 8 years from a specialist lender. Monthly £205, total cost over 8 years £19,700. Option B: wait 4 years until mortgage fix ends, consolidate into remortgage at whatever rate prevails. During those 4 years pay minimums on unsecured debt = approximately £11,000 of additional interest.

Option C: snowball/avalanche the unsecured debt, paying aggressively from current income. Monthly £400 clears the £14,000 in 3.5 years with approximately £2,400 interest. Option C is cheapest but requires the cash flow Priya may not have. Secured loans (Option A) are often the right answer when the primary mortgage cannot be touched due to ERC, and unsecured rates have become too expensive — they bridge the gap until the main mortgage can be restructured.

FCA Rules and the Adviser's Duty

Under MCOB 4.7A and Consumer Duty, a mortgage adviser recommending debt consolidation must document why the transaction is in the client's best interests. This includes: explicit comparison of total cost over the full term of the new mortgage vs the natural repayment of the existing debts; discussion of the security transfer risk; and alternative routes (debt management plan, IVA, secured loan, balance transfer) where appropriate.

The FOS has upheld numerous complaints against brokers who recommended consolidation without performing a proper total-cost analysis or without documenting the client's commitment to changed spending behaviour. Compensation has been awarded at tens of thousands of pounds in individual cases. As a borrower, ask your adviser for the written cost comparison in total-cost terms, not just monthly. If they cannot produce it, that is a red flag.

Mortgage consolidation is also a trigger for affordability reassessment. The new mortgage balance plus the new product is fully stress-tested. If the consolidated amount pushes you over 4.45x income or into a tighter affordability zone, the application can fail — which at least forces a reality check.

Alternatives to Consolidation

Five routes that are often cheaper or safer than consolidating into the mortgage. Route one: 0% balance-transfer credit card for high-rate debts. 18-month 0% offers with 3% fees work out at roughly 2% effective annual cost on a 18-month balance, vastly below credit card APRs. Route two: lower-rate personal loan. Personal loans at 6% to 9% APR over 5 years cost less than spreading debt over a 20-year mortgage.

Route three: debt management plan (DMP) through a free provider such as StepChange or National Debtline. Creditors typically freeze interest and accept reduced payments. Route four: Individual Voluntary Arrangement (IVA) for serious debt (£20,000+) unsuited to DMP. Route five: secured loan at 7% to 9% that does not disturb the current mortgage; accepts the security risk but avoids ERCs and affordability reassessment.

Non-profit debt advice (StepChange, Citizens Advice, National Debtline) is free and impartial. Paid "debt consolidation" firms often steer clients to their commission products, which are almost always worse than free advice routes. The FCA has taken enforcement action against several high-pressure consolidation firms since 2022.

Decision Framework

Consolidate only if you can answer yes to all five: (1) you have stable income with low variance, (2) you have a documented plan to clear the consolidated amount within 3 to 5 years via overpayments, (3) the underlying cause of the debt has been addressed (behaviour change, expense reduction), (4) you have at least 3 months of emergency savings to prevent future borrowing, and (5) the total-cost analysis, done honestly over the full expected repayment horizon, shows consolidation is cheaper than alternatives.

If any of these fail, prefer a shorter-term solution: balance transfer, personal loan, DMP, or secured loan. Preserve the home as genuine security rather than paying a 20-year interest bill on what should have been 2- to 3-year debt.

Finally, monitor after consolidation. If credit card balances begin rebuilding within 12 months, the consolidation has failed structurally and the underlying behaviour needs professional help. The FCA Consumer Duty obliges lenders to monitor consumer outcomes; if you are in this situation, contact your lender's vulnerable-customer team.