Jeff,
Seems that Bristol specific events are a bit thin on the ground in September at least those organised on a national level. The owner drivers association don't have anything listed but the Bristol Owners Club do have a few in the calender.
The Goodwood Revival is listed 8-10th Sept as quite a few members attend, there is also a Bristol contingent planed for the Haynes Rare Breed 100 show held on the 3rd Sept at the Haynes Motor Museum in Sparkford, contact for that even is Peter Campbell at
wessex.sec@boc.net.
If you are into golf on the 24th Sept there is the BOC Golf Day at the Dulwich & Sydenham Hill Golf Club in Dulwich contact for that is Anthony Spooner on
acspooner@btinternet.com
If your stay should run into early October I can throughout recommend the Castle Combe Autumn Classic on the 7th always well supported by Bristol owners, again the contact is Peter Campbell.
Depending on what part of the country you are staying the BOC may have some regional events organised on a local basis.
Geoff.