Several top British photographers run photographic liveaboards both at home and abroad. Videos and books on how to take decent underwater pictures abound. Strangely, training in marine biology is not as widely available as you might have thought. The BSAC runs a marine identification course, as do local branches of the Marine Conservation Society. Several independent organisations also run courses - from recognising a sea urchin when you see one, to gaining an understanding of more complex marine ecosystems.
Some universities offer extra-mural courses.
For advanced divers, the idea of doing some more demanding diving could also appeal. If you want to get more technical about your diving, extended range courses, trimix or perhaps even a rebreather certificate can all be completed in Britain.