Make sure you have all the required aircraft and pilot licensing documentation with you.
Ramp checks are not uncommon and I have seen British pilots unable to take off due to not being able to documentation not being in order.
Be sure to have the aircraft noise certificate with you, it will save you money on landing fees.
I have also heard of the ramp checkers asking to see the load sheet for the flight, while not strictly necessary for private flight I keep a selection of computer generated load sheets in the aircraft to cover most likely scenarios and the production of one of these would no doubt supply enough info to keep the box tickers happy.