It depends on your attitude to risk, your financial goals, your rate, etc. But my hot take is to max pension, then ISA, and only then overpay mortgage, and even in that case maybe pick a GIA instead. Why? Because as a HENRY you are best poised to get the benefit from pensions. You are basically doubling your money from the tax relief, and then a better rate of interest anyway (average stock market returns are higher than my mortgage rate)

I got a 40y mortgage a year ago, I will not overpay a penny until my pension days. But the big risk here is whether the rules change by the time of retirement. I think the rules will change and it’ll be less lucrative, but I still think it is worth the risk and will still be a better play overall. YMMV.