Sterilization reversal is not normally available on the NHS unless there are some mitigating factors. Your GP will know what the local policy is in your area and is the best person to speak to first.
If NHS treatment is not available then your options are to go privately through a healthcare supplier like BUPA, or to look at other options for fertility such as egg collection/sperm aspiration depending on the type of sterilization you need reversed.
Costs can be high and will vary according to the supplier so it is worth shopping around. Have a look at this site: here
You should also be aware that success rates vary too. So this is something to think about before committing to a procedure.
As the procedure is not commonly performed then patients often need to travel to get the expertise and hospital equipment.
Nuffield at Cheltenham seems to be the closest: here
I would suggest that you contact them after the weekend to discuss whether they can meet your needs and give you an approximate price..