We went to Butlins in Bognor for a midweek break when DD was 3 (4 yrs ago). Will never go back.
I have never seen so many people chain-smoking and swearing (generally whilst manning a pushchair) in my life - I didn't think I was snobby til I went to Butlins (we did Pontins when I was a child and we loved it) but that was awful.
Our accommodation (silver apartment) was actually loads better than the damp gulag we stayed in at Centerparcs, so we were happy with that, also the food in the pub and the hotel restaurant was really, really good (rest of the time we s/c or ate out), also the children's activities were great and DD loved the free rides. Pool was freezing cold so we only went once, which was a shame as it looked like a good complex, just too bloody cold!
However, I found it depressing and largely because of the people there. We saw fights break out most nights, the showbar place was filthy, packed to overflowing and stank - we just about got a table one night for the panto show and had to leave it was so horrible - DD couldn't see a thing so she wasn't upset - and the canteen, which we had to walk past to get to the pavilion, looked like hell on wheels - massive, massive queues (I hate to have a set time to eat so could not have been doing with that) building up an hour before they were due to be let in to eat and, walking back afterwards, looking in the windows and seeing piles and piles of plates still heaped with food being chucked by the cleaning staff - the food looked grim but we couldn't work out if it was being left because it was awful or because the helpings were so massive people couldn't eat it all (and waste depresses me too). Having to walk past a massive amusement arcade (another pet hate) to get anywhere also irritated me.
So it's not for me. DD liked it but not enough to want to go back - she lives in the pool normally and it was too cold for her - so thank God we never have to return!
And Bognor appears to be caught in a wind-tunnel - we went up the coast to Brighton for a day out and it was so hot compared with Bognor we couldn't believe it!