There's other camera fairs, I think Potters Bar and Orpington. I don't go to the Beaconsfield one but know people that do who say it's similar the Wolverhampton one I go to. In the years I;ve been going to Wolverhampton there's less and less LF equipment and I've never seen a 10x8 filed camera.
As a format 10x8 largely disappeared here in the UK by the 1930s with only few new cameras being made, half plate and whole plate were more common and 5x4 ruled the roost.
You may remember Kays Catalogues, I new the chief photographer in Worcester, every image (transparency) was shot to final print size, the largest was 10x8. The big catalogue companies like Kays, Moores, Army & Navy, and a few others were the main buyers here in the UK for 10x8 cameras. Kays photo department had quite a few studios and each might have a few sets, so lot of LF cameras.
So there's never been a lot of modern 10x8 equipment in the UK and what there is is almost all monorail.
Ian