Hi Mark
Spa is MEGA!!
My 1st time this year to WEC at Spa & providing you have a good warm coat (when it snows..) & a polo shirt (when its sunny....) all in the 1st hour...….!! together with a walked in pair of boots you should be fine
GA tickets get you all the grandstands including above the pits (bar /restaurant area above the pits on race day you have to buy tokens, redeemable against food /drinks but 2/3rds of it are free access)
Access to around all the Spectator areas of the circuit with an absence of Le mans type corporate hospitality areas getting in the way
The big plus for me was the vast areas that are AM photographers friendly, with many areas above the dreaded catch fencing
I've booked to go back already