Gents, I found this
map which shows Stowe circuit being in the middle of the GP section?
I was there for my CSS level 1 with Freak on the national which goes down the main straight, through the Copse right hander, into Maggot's curve which for the national turns into a right hander leading down Club Straight, into the Brooklands left hander and here's where the map is good for cars but not bikes. Instead of continuing through to Luffield there is an entry to a chicane before Luffield for the bikes and it brings you out right in the middle of Woodcote corner and then onto the straight.
I've done the full GP circuit and the national but never the Stowe circuit. If that is truly Stowe in the middle then it doesn't look overly interesting! I'd rather go to Rocky, and I crashed there on my level 2!!