Hi reg. By coincidence, a similar model was pictured "Just a Picture" by Dipstick, which I reckon is a very fine example. You can see what TerryG describes. That bike also has a front mudguard stay, your bike has the fork stay mount lugs, so you may find evidence of of one being originally fitted. The later mudguard is more round in profile, no front stay, single bolt rear fixing.
As BSA changed and evolved the design, parts from different model years can be mixed and matched, and you can choose to stick with strict model year components or just produce a working machine for the time being with whatever parts you can easily obtain.
Welcome along, head over to the intro section, spill the beans.
Swarfy.
