You will need to ask your counsellor - they will be able to tell you about the closest Superdrug which will do it. Thye need to have a lighter life trained person there, so not all superdrugs do it. You can get started with them, but only if you are not on any medications and your blood pressure is normal. If you are taking medication you need to see your doctor - because you can bet that the amounts of drugs you need will fall as you diet changes.
Superdrug will charge you around £40 for the initial visit and form filling and £5 each time you go for a blood pressure check.