I'm in East Anglia, so I might be able to suggest some options in Norfolk but some more information would be useful:
How many people are in the group? (It can make a big difference as to whether there are just a couple or a family of six!).
How old are they and what are their interests? (It's not much use suggesting a bird-watching holiday, in the middle of the countryside, for people who only want funfairs or bingo by the sea!).
When can they travel? (If they're restricted to the schiool summer holiday period it obviously restricts the options).
Have they got a car? (It's pointless suggesting a campsite miles from a station, or from the nearest tourist attractions, if they haven't).