What level of snowboarding are you and what do you prefer? Park, freeride, a lot of pistes?
The closest place is probably the 'Vosges' in France, very low mountains (the highest is I believe 1400m. You may know the 'Grand Ballon', Tour the France passes there almost every year.) Pistes are small, lifts are ok. Good area to learn. Crap if you're level is hihgher. You'll feel yourself limited.
IF you ride further south to the alps, you can go to alot of places. Chamonix is the best place for freeriding. Be sure to take a guide(!) and you'll not regret it.
For park: I heard alot off good things from Mayerhofen, Austria. Avoriaz is also pretty good for park minded riders who like a mountain too (check youtube vids from Avoriaz 'stash'). Avoriaz is part of the 'Portes du soleil'. Wich are basicly different resorts grouped togethers with lifts from one resort to another.
If you want a very big terrain check out 3 vallees in France. The total pistes lenght ia around 500-600km orso I believe. Very fast skilifts, skisure area, all types off pistes from beginner to high intermediate.
I`m pretty sure you'll find something comforming your needs.
PS: if you are in the higher part of the UK, possible some scandinavian snowboarding is possible too. But I`ve never been there