FWIW learnt to dive 18 years ago in the military, BSAC is the way to go. PADI ( Pay And Dive In ) is ok but just a commercial model, every step of training cost more.
BSAC has more thorough training and is centred around the club, pay your club fees and BSAC membership then get further train free.
Dived around the world and never had a problem with BSAC not being recognised, in fact as has been said further up more respect is given usually.
Some of the best diving can be found around the British coast, NW Scotland, IoM, and Ireland have some amazing sea life and soft corals. St Abbs is good for laying on your back next to the rock face and watching the Guillemots dive bombing for fish, and if you like the idea of wrecks then Scapa Flow in Orkney is a must.
Something to think about is open circuit SCUBA or closed circuit rebreathers, If I was starting out again I would probably go the rebreather route as its like learning to dive all over again and the kit is expensive, but rebreathers allow you to get a lot closer to the sea life.