Fk mate, that's bad news, sorry to here it, poor bloke.
Only my opinion, but if you've got time and energy I'm sure selling the stuff individually would be better, or at least divided up into Brit/Jap/US or whatever, so that buyers with a bias one way can just buy what they're interested in...
Sounds like a big job though.....if I was closer I'd offer to help.
Pretty obvious, but don't let on that you're desperate to sell....will only push the price down, don't know his circumstances but if he's got family etc he might want to sell for good prices to help them out??
Gumtree seems to get good results, some prefer it to ebay.
Good luck with it all mate, and my sympathies.
Peter.