Ron, I said that I knew nothing. I've always been used to 1/4" BSP at both ends...always found it odd that BSAs had 1/8" taps as I imagined a tiny tank thread...I now understand that there is a reduction with filter. The filters on the 1/4" taps are a nuisance as with the slightest distortion, they catch on the threads and twist.
My M20 came at 'demob' with 3/8-1/4 BSP tank adapters and taps that were 1/4 x 1/4 BSP at both ends....So at some point REME were making the change...Ian
