Rare record price guide

Apologies if this is posted in the wrong place, but im trying to gain a valuation of a couple of records. Ive had a good search around the net and i cant seem to find anywhere thats sold one of them in particular.
They are 2 BBC Transcription Discs. The first LP is from 1975 and features Queen at the Hammersmith Odeon i think. The other is one that i never see on ebay or anywhere else and it is the Transcription Disc from the Golders Green Hippodrome London in 1973. Both records are mint.
Has anyone else ever come across these before, and if so what kind of a market price would you put on records like this?
Thanks.

EIL has sold the Hammersmith LP for £300.00, but remember that EIL is VASTLY overpriced.

I bought a copy on Ebay a few months ago. I bought it for $10. I think it was a bootleg version though.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=140115680740&ssPageName=STRK:MEWN:IT&ih=004

This is the one I bought.

Thanks guys. The Hammersmith disc is defibately more common, and i think £200 - £300 on a good day is probably about right.
Im still not sure about the Golders Green disc though. I bought it about 16 years ago, and havent seen a copy around on the net. If anyone sees one anywhere it would be great to hear about it, thanks.

Head over to here: http://www.queenzone.com/queenzone/forumnew/forum_topic_view.aspx?Q=1027435
and ask Greg (Queen Archivist) if he wants to buy/hire the disc from you for a negotiable fee

Cheers for the advice.
Ive left a note on that thread and hopefully Greg will pick up on it. Sounds hopeful as he's already mentioned there that he's been looking for an official copy but to no avail.
Hope thats the best way to get in touch, any other way to contact this Greg guy? Cheers for your help.