Here's a link to the Flyer directory of flying schools:
http://www.flyer.co.uk/directory/index.php
I have experience of the BA Flying Club and Wycombe Air Centre at Wycombe Air Park/Booker, both of which are good outfits within easy reach of Uxbridge.
www.bafc.co.uk
www.wycombeaircentre.co.uk
sB
