I fly from the Prestwick Flight Centre on the North side of the airport. I must admit that I have never been held up with 757's doing circuits!. The Flight Centre only charges from Take off to landing plus 5 minutes for taxying. This is by far the cheapest option. Give Suzanne at the centre a ring and she will explain everything. They have Grumman aa5a's and assorted other things. Telephone 01292 476523.
Maybe I will see you there sometime!!