OK, non-customs airports are much cheaper, but that is not an option flying in/out of the UK.
Well, I do that as well. Poitiers, Caen, Cherbourg, Abbeville, Beauvais, Pontoise, Calais, Troyes, to name a few, are all around the eight to ten euro mark (though it's a while since I was at Calais) and all have customs. Some notice required, by phone, except for Poitiers, Cherbourg, and Calais. Oh, and the free landing and hangarage at Thionville, where they say they have customs as well.