Today, two registries made announcements that are clearly targeting registrants of the co.uk ccTLD.
Nominet, the .uk ccTLD Registry announced the availability of second level domain names, such as encirca.uk. Note however, that all existing third-level .uk domains, such as encirca.co.uk are grandfathered in and have first dibs on the corresponding second level .uk domain name.
At the same time, the co.com Registry, announced the release of thousands of previously-reserved domain names. According to the co.com Registry, they are seeing a lot of traction from registrants in the UK for co.com domain names.
This makes sense, since the public in the UK is accustomed to third-level domain names under co.uk.
The choice comes down to one of branding. A business can elect to be branded with a .uk identity or a more global identity.
There are lot of great generic names available. the full list is available here:
Register your co.com domains here: Apply for co.com