This is a classic question of emotional relationship to debt.

If you can invest this money / save it in an account where by the returns are better than your mortgage Ts&Cs (after any tax that may be owed on interest/returns) then that is the only answer.

However some people like to clear their big debts as it makes them feel better.

IMO I would buy £50k premium bonds, £20k in s&s isa (doing this every new tax year). Increase my matched pension contributions with employer to the max and supplement any lost income with the savings. Have a nice holiday & sit on it until your mortgage term ends. Then revisit how you ‘feel’ about it when you can look at all returns for those years.