Well I expect you are already aware of the vintage erotica forums that deal with mostly British stuff
Vintage Erotica Forums and there's also the "British Girls Adult Film Database" forums
https://www.bgafd.co.uk/forumindex.php but they could both serve as a good resource for 'jumping off' and finding material which is specifically British orientated - They do have a lot of members that are magazine collectors, from the days before video
