Nominet is the authority for all UK and Welsh top level domains (TLDs) and a number of second level domains (SLDs). They are the registry that store all the pertinent information about a domain ie who owns it, who is repsonsible for it and which name server control its behaviour. Registrars must be Nominet members to register a domain name directly with Nominet.

TLDs
.uk
.cymru
.wales


SLDs
.co.uk
.org.uk
.me.uk
.ltd.uk
.plc.uk
.net.uk
.sch.uk
.ac.uk
.gov.uk
.parliament.uk
.nhs.uk
.mod.uk
.mil.uk

Find out more about Nominet here www.nominet.uk

Check ownership of a UK domain at Nominet here www.nominet.uk/whois