Unless you've got the funds to spend a fortune on training, you're probably going to have to join the Red Cross or St John's:
http://www.redcross.org.uk/branch.asp?id=425
http://www.sja.org.uk/counties/county.asp?coun tyCode=BDS
I'm glad that you understand that there can be different rules for first aid when immediate help isn't available. I remember taking a first aid examination when the examiner asked me whether I would ever give a casualty anything by mouth. The 'standard' answer (in basic first aid training) should be 'No' but I told him that if I was stuck on a mountain (with a long wait for help), with a casualty who'd broken his leg and was showing signs of shock and exposure, I'd definitely give him a Mars bar to boost his blood sugar level.
It turned out to be the right answer. The examiner didn't know about my Mountain Leadership Certificate and I didn't know, until later, that he was the doctor for the local Mountain Rescue Team ;-)
Chris