C15 mudguards to me, are a bit of a mystery at the moment, I bought a new reproduction one from a firm in the midlands which was supposed to be for this model but found it to be too shallow, being only 2" deep instead of 3" and it seems the radius is wrong, after checking the other types of mudguard it appears that the mudguard for the bantam is nearer to the original C15 size.
I am just wondering now whether to just patch up the existing guard or try another type.
Tin ware for these bikes is becoming rare. I am surprised no one is remanufacturing tin ware as these are very popular bikes so I would have thought it would be reasonably economical to make reproductions. I know some panels are produced in India and I believe there is some one in the West Midlands importing them and selling here. I did buy a reproduction number plate holder for a B40 but the quality was poor and the welding was very bad. I also needed a new rear mudguard but ended up welding and patching it myself to a satisfactory standard. It may be better to get yours repaired. The C15 and B40 have particularly deep mudguards and all the pattern ones or universal ones are not deep enough.