There's a campsite at the NW corner of Coniston, can't remember what it's called with access to the Lake. There's also one NW (but more W) of Windermere - I think that one is run the the National Park, or National Trust or something like that.
My sis went somewhere really nice in France last year that had lovely lakes and countryside. Site offered caravans, chalets and camping. If you are interested I'll email her and find out what it was called.
I also like to do this jema, several of us mums dump the dh's for a week in the summer hols and go off with the kids.
Lake Bala is good, quite shallow by the side of the campsite.
Also Keswick (Lake District) has a nice Camping and Caravanning Site at the side of Derwentwater but can get very busy and gets booked up early - also a risk of being cancelled due to flooding which happened to us last year. Lovely there though.