if you're looking for basic, but with great location there's one in tenby that's only 10 mins walk (carrying a toddler, lol) from the beach - although it's more like 20 mins on the way back, it's at the top of the hill
we went out of holidays and there was just us and one other tent.
Oooh oohhh have a look at Middle Woodbatch Farm near Bishops Castle, Shropshire. Check out UKcampsite for info. Have to dash now but it was so lovely and only 10 pitches in a field on a working farm. We will be going back.
Tir Bach in pembrokeshire -v.small site about 20 pitches and 2 yurts,lovely views, friendly farm animals and clean loos, shower, washing up block South Penquite farm on Bodmin Moor, about 10 miles from north cornwall beaches - again a few pitches for tents only and 2 yurts, fantastic solar powered shower block, great views and friendly sheep dogs Find on google