Not a lot of information out there that I can find. www.belltarget.com is a useful site that has a pdf file of a very interesting book "ring my bell" by Frank Spittle (apparently no longer available).
Couldn`t find any mention of bell target in the north of England or Scotland, seems to be mostly around Birmingham/midlands area .
Matt`s video on you tube is an excellent piece of work and well worth a watch if you haven`t seen it already. Can`t be that many Britannias kicking about now and probably more expensive now
Seems to be a bit of a resurgence going on at the moment with a few new clubs starting up, good to see ,especially if the old vintage rifles get an "airing".
John