The requirements for a private flight within the UK are simply that you
a) have to be able to produce certain documentation within a reasonable time (you don't have to have it with you) -- C of R, C of A, crew licences.
b) have obtained enough information to reasonably satisfy yourself of the things Art 43 require -- these include information about the weather and airports to be used, that the aircraft is serviceable and required equipment is carried, that the W&B is OK, that you have sufficient fuel and that the performance of the aircraft is capable of meeting the challenge you are about to confront it with. Nothing has to be written down.
I imagine the vagueness of the requirements make ramp checks difficult.