Thanks for the 'heads up' for another source of fasteners, always worth giving a call out for good suppliers for, what now appears to be, dwindling stocks of imperial fasteners.
When I was working in India (pre-Covid) I was pleased to find excellent supplies of both Whitworth and BSF SHCaps, Mush heads, countersunks, and hex headed machinery bolts; the BA's were more difficult as they seem to have been overtaken by Unified # screws. Admittedly, there were good and bad quality manufacturers, but the locals told me which ones were the good ones and which to steer clear of.
As an aside to this I found it was curious that the socket sets used in India were either 1/2" or 1/4" – they had never heard of 3/8" sets. I explained that 1/2" was for Tractors and trucks and 1/4" was for bicycles and washing machines! 3/8" was for cars and engines. I took them a few sets out for their use – they were fought over like prizes from the gods.
Martin