For future reference, the little screws holding those latched to my (Aus) 11 set are 6BA. In case anyone is in need of BA fixings, I have been using this small, helpful, friendly firm
http://www.ba-bolts.co.uk/
I bought two of Kevin's £50 Ariel coupling units (one for a friend) which is the first time I have owned a complete and un-molested unit. He also sent this link to an auction where an identical unit sold for £500 #71 and a WS11 for £1500 #93 .
http://auctions.durrants.com/auction...page=2&aid=288
Ron