What to do with extra cash when mortgage repaid?

Im currently 51 years old. My mortgage will be repain in full by my 59th birthday. At that point I will have circa £700 spare cash each month between age 59 and 65 when I retire. I want to understand if this cash should go into my pension or should I put it in any other type type of investment.

I currently have enough cash sitting to cover six months of bills.

I currently have a defined contribution pension to which I am paying in £600 per month including the maxed out employer contribution. Aged 65, the projected value on an average return is £350k. I plan to take some of this sum out tax free to see me through to state pension age at 67.

I dont have any other investments and am unlikely to have much spare funds to invest before the mortgage is paid off at age 59.

My specific question is, one mortgage free, would I be better putting the freed up cash into my defined contribution pension to help with compounding?

Or should I invest this money elsewhere to avoid having all my eggs in one basket?

Thanks in advance?