Does it specifically have to be a campsite? I've stayed at the Bradford PC bunkhouse at Brackenbottom, Horton in Ribblesdale which is really good, at only Â£4 a night. I'm sure leaving your lamp on charge wouldn't be a problem!
Have a look at http://bpc-cave.org.uk for more info.
If you have a caravan try New House Caravan Park, Cowan Bridge, on A65 10 mins from Ingelton Nice site which stays open all yaer round for about a tener a night that includes hot water showers elect and the cleanest loo block you could ever wish for
The name of the guy is Colin its best to ring before hand a must out of summer season tel 015242 71590