Well we went to Haven last week and had a fab time, i definately recommend going for a cheap holiday with little ones. I wasn't sure what to expect as i had never been anywhere like this before(Butlins adult weekends don't count!) but it was lovely, our caravan was bigger then i ever expected, the staff were friendly and it was incredibly clean.
Sadly we didn't get to the beach as the weather was awful for us but it looked nice!
Seb was entertained by the soft play, swimming pool, shows and rides
Food was also great, there was a kitchen in our caravan with everything you could need but also a fish and chip shop on site(proper seaside food), as well as a pub which served breakfast with the characters, lunches and dinners as well as huge sundaes
We've already talked abvout going again next year, it would be really easy to take a baby there and Seb would be able to join in more of the activities, as they also had kids clubs etc
So thumbs up to Haven!