Investing vs paying mortgage off early

Fatbritabroad

Hi new member here

So I wanted to get some general advice. I got divorced two year ago but was in the very fortunate position to keep the house. I was left with a large mortgage of 325k . I am paying this off by overpaying 500 a month as I'm keen to get it down to a more manageable level while rates are low and also have a lodger ATM which helps.

My question is would you say its better with current rates to save or invest the money in pensions and isas to use this to pay off early at a later date or pay it directly. When I remortgage next year I can expect a rate of 1.39% so was thinking much better to invest and say mortgage down to 25 years (currently 33) which will keep my basic monthly payment the same but reduce the term by 8 years

Fully appreciate I'd need to invest for at least 5 years but I'm anticipating rates will remain low for a while yet

I put a lot in a pension as well and save about 18% of my income in it. I have 100k already and am 35. Wasn't sure whether to scale this back and invest or save more to clear the mortgage quicker

Any advice welcome