Why would it be any of their (French custom's) concern whether you paid VAT in the UK? Are you importing the aircraft into France or are you just transiting, in which case I believe no duty must be paid in France or anywhere else?
I take my glider regularly to France (albeit by road trailer) and I cannot prove that I paid VAT on it either since I bought it second hand and hence VAT exempt.
Ciao,
Dg800
Last edited by Dg800; 17th December 2012 at 12:21.