- SSI/PADI: get your Nitrox cert, maybe AOW, gets a double set and drysuit get some diving done,
- BSAC: join a BSAC club and get some diving done, progress to Sports Diver and get a set of doubles and maybe get accelerated deco, then progress towards other technical classes
- GUE: get Rec2/3 then a double set/drysuit training, get some diving done
- SDI/TDI: progress towards drysuit and doubles, Nitrox, get some diving done, then intro to tech (or ANDP directly if you are quite confident)
That will take you probably more than one year to get to Fundies or Intro to tech unless you can somehow do maybe close to 100 dives in that year?
You are likely to need to dive a lot locally to get this done, get to the point where you can just dive with a buddy on local charter boats. (many U.K. divers just book individual spots with their buddies on charter boats, unless they join an organised trip where the whole boat has been booked for a group)
Don’t forget to have fun on the way
If you want to have classes in a warm place, Malta and Egypt have a lot of technical instructors, and they are some of U.K. favourites destinations to do technical classes in warm water.
But you are unlikely to get enough dives in a year to reach that level of proficiency if you do not dive locally: you are likely to have to aim for more than 75+ dives a year to be able to progress towards that goal. (If you don’t please let me know if your workplace is looking for new hires /askingforafriend )