Sites run by the Caravan Club and the Camping & Caravan Club are always reliable and many are open to non-members. Have a look on their websites for locations etc.
You also need to define "good" - do you need children's play areas, access for tents, large caravans etc?
Hi Thessjjj, try giving us a list of your basic requirements and we can try and help. I personally like to be near York. Countryside on the doorstep, great shopping and eating in York.
I went here http://www.streetheadcaravanpark.co.uk/ for the last week in July.
I'm sure the scenery was magnificent but it rained so hard and so often it was hard to tell.....
I hope your weather is better than our was! :o)
The map search can be particularly useful:
http://www.ukcampsite.co.uk/sites/calcdist.asp
Simply double-click on the map at an appropriate point (such as on the Yorkshire coast) and use the filters to narrow down your search.