Excellent start for a project. I've just had a look at your picture and can tell you the following are not BSA.... all the fork parts, lights, exhausts, the carburettor (might work but not original), handlebar levers, mudguards and wiring harness. You're lucky to have the original footrests and brake pedal, wheels, tool box and oil tank. The petrol tank looks like a small capacity tank, either Catalina type or 'export' but it is probably A10 though there was one fitted to the A65 which is similar. I can't see a dynamo anywhere on your pics. You may have a problem finding decent mudguards if you want to build something which looks original. My best advice (which you probably don't need!) is to be clear from the outset what type of finish or overall look you are aiming for e.g. original / restored, or 'special', or just a tidy runner. If you are aiming for original / restored you will need to look very carefully at what you've got and decide what can or can't be used then think about the availability and cost of suitable parts. On the other hand, a tidy runner, can be built quite reasonably with lots of replica parts which are available. For example, Gold Star mudguards and stays are in plentiful supply (OK the quality varies) and these will look fine if you just want to get up and running on a respectable bike fairly quickly. Anyway, good luck!