I've tried accessing ICUK's ISP and Hosting company sites, they're both down for me too, though it's the first I've heard of it. Curiously I can tracerout the connection to 'www.icuknet.co.uk' without any problems, although half of the server hops have higher than usual ms response times.
It looks to me like the name servers, which are responsible for translating the server from an IP address into a human readable form - icuknet.co.uk , have failed. This usually occurs when a domain name expires or the server is being moved/has been taken offline. The domain is good until 2009 so it's not that.
Sadly all my contacts for ICUK are e-mail based and thus require the domain name to exist.