consider your tax bracket.
For example if your taxable earnings are over £50,270 (into higher rate) it may be an advantage to pay at least enough to bring you down to standard rate. You'll recall that basic rate tax is rebated on pension contributions,
and you can claim more if a higher-rate taxpayer up to certain limits.
If your earnings are over £12,570 no point in taking below that, because it's the tax-free allowance.
Mortgage interest rates are pretty low. It is generally very unwise to take out a loan, at high interest rates, to invest.
If you have at least 5, preferably 10 or more, years for your pension to grow, it's my opinion that growth over that period should be greater than your mortgage interest rate. There are ups and there are downs. For example, Brexit and Covid both caused downturns; so you had a couple of bad years, followed by a recovery.
In some cases, such as America's Great Depression, or Japan from 1990 to 2020, recovery took much longer but this is rare.
As Mottie will grudgingly admit, the European fund I bought into prior to the Brexit referendum is now up 94% between 23 June 2016 and 27 Sept 2021. This is a bit of an outlier, though. The FTSE100 is up 9% over the same period. And I still have some shares in National Grid, which are down 24%. So the best advice is to buy a low-cost tracker fund which will even out unusual events. If anybody tells you that the Fund Managers at WonderCo always beat the market, they are wrong.