I'm going in mid May, and will be camping at a Haven site, Thornwick Bay which is about a mile and a half from Bempton, an easy walk along the cliff path. At the moment a standard 2 bed caravan there for 7 nights arriving Friday 15th April will cost £180. Log on to Haven.com and for offers at Thornwick playing around with arrival dates, you may find cheaper. Mid April to may seems to be a fairly good time for gannets and Puffins. hope this helps.
cheers Terry
my photo's here