Hi MrZet...... there was a good one set in a wooded glen at Kirk Michael, turn left at K M on the coast road to Peel, campsite not to far along on the right..... If I remember rightly the seashore was only a short walk at the back of the camp site, plus local petrol station, pub and shops.
As sdv9r says check it out with the Tourist office to confirm it's still open.