If you need some up close photos of a BSA sidecar I have one and can snap a few shots.
I also have a 1929 sales catalog from BMS that has photos of the chairs and a short discription. from the photos i can see that mine is a No. 7 as it has a door and a locking trunk, the shape appears to match mine.
You may want to contact mark upton at british only austria as he has a few boats and bodys about