I've never seen a .net.uk before, do they exist?
I've owned a couple, back in the days when I owned an ISP/Hosting company. They are for network providers, and rules have been tightened.
< direct from Nominet domain rules >
11. Specific rules for the .net.uk SLD
11.1 Introduction
These are the specific rules for the .net.uk SLD, administered directly by us. They form part of and, in the case of conflict, take precedence over the Rules.
11.2 Requirements on Applicants
11.2.1. This SLD is reserved for the computers of network providers, that is the network information centre (NIC) and network operation centre (NOC) computers, the administrative computers, and the network node computers.
11.2.2. Registrants in the .net.uk SLD are required to be Internet Service Providers. Notwithstanding the Rules, no Domain Name shall be registered in this SLD unless, in our reasonable opinion, the applicant is an Internet Service Provider and the Domain Name registered is the same as or a similar variant of the applicant's name.
11.2.3. Without prejudice to any other test that we may apply, the applicant shall only be deemed to be an Internet Service Provider if:
11.2.3.1 the applicant is either:
a company listed on the Register of Companies at Companies House in Great Britain under the Companies Act 1985 as amended from time to time or on the Register of Companies at the Northern Ireland Companies Registry under the Companies (Northern Ireland) Order 1986 as amended from time to time; or
a partnership as defined by the Partnership Act 1890, Limited Liability Partnerships Act 2000 or a sole trader; or
a United Kingdom government department, local government body, or associated government funded organisation; or
a recognised academic institution geographically located in the United Kingdom; or
a Charity on the Register of Charities at the Charity Commission in the United Kingdom;
11.2.3.2 AND the applicant either:
is listed as a local internet protocol (IP) address registry with a regional IP address registry; or
has an Autonomous System containing hosts in the United Kingdom that is listed with a regional IP address registry and that is
continuously or at all reasonable times reachable from major Internet exchange points.
11.2.4 Any Domain Name registered in .net.uk may only be used in the manner set out in this Clause, and we may suspend or cancel the registration if we believe it is not being so used, in accordance with the termination provisions set out in our terms and conditions.
11.2.5 The Domain Name must not be used in connection with any service provided by the registrant on behalf of any other entity. For example, the Domain Name must not be used as part of another entity's e-mail address or URL.