There's been another major update to the TZX Vault, a site dedicated to providing "exact" TZX images of ZX tapes and disks (and expanding to provide Amstrad, C64, Vic20...). There's loads of updates, certainly too many to list here, so well worth a look for that elusive rare game you're after.
And on the subject of rare games, the team are expecting this to be the last major update for some time - it's getting expensive purchasing the rare tapes from the MIA list, just to fill in the gaps. So if you think the Vault is a good site, why not help out -- at the very least check in your attic to see if you have anything they need.