The first thing to do is check your state pension. Call the future pension centre at the DWP and ask for a pension statement.
They will tell you how many qualifying years you have for a State pension and how many you need to qualify for the full rate, they will also give you advice on what you can/should do to top it up if there's any shortfall.
If there are any gaps, you can make a voluntary payment up to the previous 6 tax years to top up your credits.
There's also home responsibility protection that LOADS of people haven't claimed (see Martin Lewis website for more info) this can increase your SP too.
Secondly, you need to look out all your old paperwork for historical private/workplace pensions. Check with your bank for offers on private pension pots and combine them all together. (monzo do a good rate and all the leg work for you)
There's no point in having small pots all over the place, they will loose value. The best move is to combine them now and invest them with your bank or similar, I.e monzo, money box or similar.
You should also try and opt back into your workplace pension scheme. Set it to the lowest rate and you should hopefully be able to afford the monthly loss without it having too much of an impact. Your employer will match your contributions up to around 5-6%
Did you say you are over 40? A LISA is a must if you don't already have one. You can open them before you reach 40 and as long as you pay in before your 40th birthday, you can continue to pay in until retirement. Even £10 per month will build up interest and you can set the "round up" feature on your current account could put a little extra in with every spend you make. That way you wouldn't really notice the difference.
You would be looking for a long-term investment plan rather than the short term used for a mortgage with the government 25% scheme. This should give you a better pot when you do come to claim.
Good luck OP. It's never too late to make plans for the future, even if it's only baby steps, it all adds up.