Yes, there is definitely a real chav element there. But I also have friends with children in private school who take their girls there as their girls love it.
Also agree that the hotel at Bognor is the best way of doing it. Accommodation is actually quite nice.
There is non stop entertainment if you want it - usually you'll find a full blown panto / other big show each week, lots of mini shows throughout the day, puppet show, soft play, swimming, indoor rides for smaller children, fun fair rides for bigger children, organised activities for older children and families etc etc... All of this is free.
There are activities that you can pay for on top, such as bowling etc, but we never need to. We also try to get off site for a few days... because we need to 
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If you have children who love the characters (angelina ballerina, bob the builder etc etc), evening discos, soft play and swimming then they will have the time of their lives. For you - take a good book .
As for price, Butlins is cheaper if you book way in advance. I booked a year in advance and paid £650 for a mon - fri visit in the hotel with dinner bed and breakfast. It was over £800, to book the same week at the same time for the basic accommodation at CP. I know we checked! That's not even including any activities at CP. That said, we still go to CP each year.
Agree Butlins is best for 3 - 8 year olds. I have a 4 and 7 year old daughters - they love it. We go each year for 'their' holiday and then to Cp for us.