I have been to Hafan Y Mor in North Wales which was pretty good. It was about 5 years ago though.
It was originally a Butlins. It is a VERY large park and does seem very spacious, plenty of room to stroll around.
There was loads of entertainment for all ages and a great swimming complex.
It is on the Lynn peninsula and near Snowdon and the national park so there is plenty to see and do if you like the outdoors (in fact it is a great base for a walking holiday)
There is a small beach (not I great one I have to add) and also some interesting nearby towns such as Porthmadog and Criccieth (with castle).
Portmeirion, the fantasy village, is also nearby (home of the TV series The Prisoner)
http://www.portmeirion-village.com/
You can read more about the camp here
http://www.havenholidayhomes.co.uk/index.cfm?p age=1067&group=hafanYMor&wt.svl=hafanYMor