1937 BSA B21 250cc OHV Single. Running Barn Find Project. Girders. Pre War

1937 BSA 250cc overhead valve single. B21 model I believe.
Running barn find with no docs. The lights were lighting up even without a battery indicating that they were running direct off of the dynamo. Here is a short video of it running.
https://youtu.be/7Ci-kOqELHk
The engine sounds OK and there is good oil return. As you can see it is completely unrestored. Something tells me that this might be one of those where leaving it alone might be a good option. Anyway, there it is. Yours to ride or restore.
Viewing is welcome 07718 583259. Collection preferred, but I can deliver to your door for £ 140 in the mainland UK by courier. No Paypal or credit cards.