It probably depends on whether you like a very quiet site, or one near a town or village and with more amenities, entertainment etc. It also depends on whether you are using a tent, caravan or motorhome; some sites cater for just one of these and others are mixed. For example, the Caravan Club sites are nearly all excellent but they're only for caravans and motorhomes.

So to find the best site for you, you should do a search. You can start with the UK Camp Site website, which is very reliable. From there you can do further searches which are tailored to your needs. For example, under the 'popular searches' tab you can narrow it down to 'tents only' 'beach' or whatever best fits your needs. Once you have a list of sites that interest you, you can read the reviews - I've always found the reviews on this site are mostly sensible and detailed, so they are generally a good guide. Hope you find something you like.