Pretty sure there's a thread on this here Nick so no doubt the MODS will move your post and mine, or redirect us to repost! However, I know at least one person who has exchanged (Diabetic, living here, no UK Doctor so had to when his UK licence was about to expire).
Time consuming and boring but not actually difficult.
However; EU legislation says you don't have to change until the licence is due for renewal. Coppers here may try to claim otherwise.....as they did in Spain in the past. Unless the law has changed recently they're wrong.