They search your bags in many places now, however, I really think stopping you from entering just because you bring a picnic lunch because you don't want to pay uber high food prices after purchasing an entry ticket, is cutting their nose to spite their face!
Just tell them it's a special dietary requirement - gluten free bread etc
Eh?
Ive taken food into the pleasure beach before. I was under the impression that the search was for security reasons, not to see if youve got a couple of sarnies in your bag.