Well, they arrived today!
Haven't got them installed properly yet (I need new seals), but put one of them on an arm. Quite impressed with them, on first impressions. They definitely are bigger than the old ones I had, but not sure how much of a problem that'll be - might just end up putting them a little bit further up my arm so it doesn't cause a problem, but i'll see.
The locking mechanism is very nice, seems very easy to get on and off, and no chance of falling off! Also can't be put on wonky, and so can't leak like my old (Hydrotech?) ones did.
Also a very good method of fixing them to the seals. Can go on latex, neoprene, or even on neoprene warm cuffs, all exactly the same method, so very flexible. And the seals aren't stretched over the outside, so should be less chance of damaging the wrist seal (which is the reason I wanted new gloves in the first place). But these took less than 5mins to fit to a latex seal, where as the old Hydrotech (?) ones i've got could easily take 30mins each side, and often much more!!!
The gloves themselves are held in with a nice firm gripping thing, so again there's nothing stretched over on the outside, and no o-rings or rubber things to slip off (which used to happen regularly on my old gloves). And nice and easy to swap new gloves onto when I put a hole in these - can take any old glove - perfect!
So yeah, very impressed so far, though obviously i'll really see when I get them in the water. But they look like they're much better than any other dry glove ring systems i've seen, comes with a DVD showing exactly how to fit them, and only £61 (follow the link to the shop from the Northern Diver website).
So thanks for the comments earlier, i'll try to remember to add my thoughts after i've got my new seals and taken them diving.
David