I think this is the plcae.. cant remember too many campsites around the lake...
http://www.lakeside-holidays.net/
looking at £5 - £6 ish per night per person, they have hot and cold water, showers etc....
after looking at google earth, this is the campsite in question.....
the place in question is very scenic, I think from memory there is a small pub on site as well, but its only a few minutes walk from the main village.... theres also a cafe near the campsite for those who dont want to cook their own food!