You have about 20 years to got, without the benifits of a company scheme were contributions are matched or better then just look for the highest rate of return you can get, bonds or an ISA. Or Gold if you are feeling brave, but beware that bubble will bust soon.
If you stick that amount into a bank over the next 20 years then you will have about £65,000 at the end assming 3% interest and you increase your deposits by about 3% p.a.
You gov pension will be about £150 a week, you can add about £100 a week from your stash over 10 years.
So gives you £250 a week to live on.
Try and find a part time 2 days a week job to add another £50
So you have £300 a week.