Any question answered...

I see.

Well then you were right with your first option, but I'd like to note a few extra cautions that should be taken.

1. New phone. New Sim. Make sure he doesn't ever receive the number.
   
2. New email. If you have a work email that he has access to, request with the IT department for a slightly different variant and immediately begin using it. i.e. instead of tenderloin@work.com, opt for t.enderloing@work.com
   
3. Get a new personal email account, choose a few select friends that you want to see again that don't live in Hounslow - email them from your new address with a note saying that to all intents and purposes you have become a operations officer for the SIS and that your former friend must never know of your continued existence.
   
4. Change your address as soon as possible. You said he's going to Nottingham until Sunday - well you probably won't be able to move out tomorrow - but Friday or Saturday should be good. To keep up the illusion of your new life, don't bring anything with you that you can't live without. Bring bank cards, passport, national insurance, drivers license etc - but only for the purposes of starting a new identity.
   
5. Arrange to change your name via deed poll - It's quite simple. it costs 15 pounds. The call is free from a landline (a payphone in your case, at least three miles from your house) The number to ring is 0800 448 8484. Do this tomorrow.
   
6. On Friday, bring the new documentation with your new name to a bank - not the same one you hold a current account with. Request that you start up a new account with them. (You'll have to provide proof of address for this - unfortunately this will mean bring a bill from your old house - bank statement/drivers license/utlities bill - mobile phone bills aren't accepted. There's no way around this unfortunately given the time scale we're looking at so you'll simply have to start the account under your new name but using the old address - then as soon as you have arranged for a new bill to be sent to your new address under your new name, contact the new bank and have them update the details.
   
   

Then you should be good to go.

Good luck.