Your five-year fixed rate mortgage is ending this month. The rate you locked in at? Probably around 2.75%. The rate you are looking at now? 5.54%. That gap translates to an extra £388 per month on a £250,000 repayment mortgage over 25 years, according to Moneyfacts calculations published on 25 March 2026.

How the Fixed Rate Mortgage Payment Jump Breaks Down

Moneyfacts data shows that borrowers who took out a five-year fixed rate in March 2021 could have secured an average rate of 2.75%. That meant monthly repayments of £1,153 on a £250,000 mortgage over a 25-year term.

Today, the average five-year deal sits at 5.54%. The same mortgage now costs £1,541 per month. That is an extra £388 every month, or £4,655 over a year (Moneyfacts, 25 March 2026).

For BTL (buy-to-let) landlords on repayment mortgages, that £388 comes straight off your monthly profit. If your rental income was just covering the old payment plus costs, the new rate could push you into negative cash flow.

And it gets worse if you are looking at shorter fixes. Average two-year fixed rates are now more expensive than five-year deals for the first time since last summer, according to Moneyfactscompare.co.uk.

Why Swap Rates Are Pushing Mortgage Costs Higher

The mortgage market has been in turmoil. Over 1,700 products have been withdrawn since 9 March, according to Moneyfactscompare.co.uk personal finance analyst Caitlyn Eastell. Unstable swap rates - the rates at which banks lend to each other - have been driven higher by conflict in the Middle East. Swap rates directly set the price of fixed rate mortgages.

"While some of these deals have come back, they are at higher rates," Eastell says. "It could be fair to assume many lenders may be taking this path, which could drive average rates up further."

Lenders are pricing in several base rate hikes. Even a single 25 basis point (0.25 percentage point) rise could push mortgage rates higher still. Borrowers on tracker deals (mortgages that move with the Bank of England base rate) will feel these rises immediately (Moneyfactscompare.co.uk, 25 March 2026).

What BTL Landlords Can Do Right Now

Around 1.8 million borrowers are expected to refinance this year, according to Moneyfactscompare.co.uk. If your fix expires in the next six months, you do not have to wait until the last day.

Most lenders let you secure a new deal up to six months before your current rate ends. That means you can lock in today's rate as a safety net. If rates drop before completion, you may be able to switch to a better deal.

The alternative is slipping onto your lender's standard variable rate (SVR) - the default rate you revert to when your fix ends. Eastell warns that moving to the SVR would add over £630 per month on average compared to the expiring fix (Moneyfactscompare.co.uk, 25 March 2026). That works out to over £7,560 a year.

Run the numbers on your own mortgage. Work out what your new payment looks like at 5.54% and stress test it against your rental income. Then consider speaking to a broker before more products get pulled.