As an ex pat who still dabbles somewhat, I'll throw this in for what it's worth:
1. Aren't lot of UK dealers sourcing their sales from existing UK collections? Therefore the prices they are having to pay are also increasing. Therefore, the mark up on these items will remain the same, no? It seems to me that it's a Catch 22 scenario with these particular records.
2. There is a large group of collectors who didn't exist "back in the day". Namely guys like me who moved from UK but took their vinyl addiction with them. We have little opportunity to buy "face to face" at venues etc so therefore the cyberworld has opened up a completely new avenue of sourcing for the likes of us. I have bought over 1000 records in the last 2 years using the computer.
3. There is a one more group of "new" collectors who are growing by the day.......The Yanks! I live here and everywhere I go the dealers/collectors who I've dealt with in the past are now fully conversant with the "British Disease" of paying large wads of cash for VG- 6Ts soul labels. There is no escaping the fact that the Rare/Northern Soul world is no longer the small (ish) corner of Goldmine and Discoveries like it was in the 70/80s. Example....I met a guy the other day with over a dozen Danny Moore's, he's asking $300 each! I tell him "Get real" he tells me.........."Get Manships book!!"
Don't profess to have an answer to finding good records cheap, just some of my observations, like Mark Bicknell said........it's people.
Nice talkin' to ya......
Regards,
Dave