If you are a nominet member then you can contact them directly and they will let you know the position. Otherwise you will need to wait for the domain to be released which usually happens 2-3 months after the name is detagged.
If you aren't a nominet member sticky me with domain name and I will look into it for you.
Nominet are not currently releasing any detagged domains whatsoever. They are now taking several weeks to retag domain names after they are in possession of all the required documentation and PGP signed emails from the renewing tag holder.
They do not have the admin staff to spend weeks chasing up usually uncontactable former registrants just so that they can make £5 for re-registering the domain for an eager would-be registrant.
I recover several detagged domains every day on behalf of original registrants as well as new registrants and if you let me know the domain you're after I can tell you the full position.
Great news for anyone who is after a .co.uk detagged domain name. Nominet have very recently started releasing large tranches of detagged domain names and they are now becoming available on a daily basis.