The last original set I saw for sale was at the Banbury run autojumble in 2019,seller was asking £150 they were the type with out the brass wing nuts, but have seen really good sets with all the brass wing nuts for £200+,I believe BSA M20 pannier frames had an extra dished washer welded on to locate the wing nut bolt when folded down for use.
Must be about 4 years ago now that I sold a full set of frame, 2 bag racks and the bottom bars for £350. Doubt you would get them for that now if the person selling knows what they are.
