No question -
Fern Bay Green reversed. Its always been immensely fun, especially the back section: uphill from the esses, a small kink, then grit-your-teeth for the left turn in - get it wrong and you scrape that huge wall... I could go on, but you know the course. Its way more fun reversed than in the other direction. I'm happy with Fern Bay Gold in either direction: well suited to the GTi.
I know its going to be against the grain, but
Westhill reversed too has always provided really fast and close racing for the GTi.
Aston Cadet is a banger racing track - only fun if you want to do full contact racing. Aston Club I could live with though. But I'd prefer any of the longer Aston circuits....

(except Aston National...)
Kyoto National is really good too.