Detagged.co.uk
YourSiteHere.co.uk
SnapNames.com
Pool.com
Depending on how much you want the domains, you'd be advised to book at some/all of the above.
Even with a slot booked at all 4 catchers, if you're going for a popular name (not the case here, most likely) then it's 50/50 whether you get it or lose to one of the private catchers running their own systems.
Is the deletion time-scale the same for .co.uks as it is with .coms, (i.e. 45 days expired, 30 days redemption period, 5 days pending delete)? I think I'll risk trying to registering a couple of them myself, but don't want to have to check the whois data every day for a month while I'm waiting for them to become available.
On a side-note, it'd be nice to see a comparison of the effectiveness of the various drop-catchers. I don't suppose there's a list anywhere of which service won which names that all of them were in for, is there?
A) The drop cycle is completely different. Domains usually go into "*** suspended ***" status and then drop around 90 days later. However, Nominet sends the registrant a snail-mail paper invoice during the suspended period, so it's fairly common for owners to renew their domains (at a premium, I might add) during that period
B) If you're chasing even modestly desirable domains, there's no way you'll beat the automated services. There are about 50 large players in the .co.uk market, and many hundreds (perhaps even thousands) of smaller players. There are at least a dozen fairly effective private drop catchers, in addition to the "public" ones I posted above. Having said that, you might get lucky if it genuinely is a name NOBODY else is after - but that's the same story with .com or any other extension
C) Re. effectiveness and metrics, Nominet forbids publishing anything to do with who-owns-what as they have very stringent terms attached to their Whois data. Having said that, if you go to the Detagged Forums you'll find some info about successful catches and which companies were behind them. In general, the "success ranking" is as I listed it above i.e. Detagged is most effective, then YourSiteHere etc. However, the market is still open enough that even the bottom of the list catcher might get lucky on your behalf for a "great" domain name.