Ryanair or easyjet reactions
OK, so you've decided to go to sunny Spain and not being a "Laze on the beach type" are going to hire a light aircraft when you get there. So far so good.
You turn up at Luton/Stansted with your case and your hand luggage, case no problem then they want to check your hand luggage (pilot case containing, headset, GPS, VFR charts of Spain) are they going to allow you to take it aboard?
I remember an episode of "Airline" where the British sky diving team had some trouble when they all wanted to take their parachutes on board as hand luggage.