If you have a .co.uk domain name, or others within the .uk domain family that is eligible. The .uk domain has been reserved for free until 25 June 2019. This is dependent on your unique domain remaining registered.
Buy it before 1 July 2019 or loose it
No one else is able to buy or register your domain’s “.UK” until 1 July 2019. However, after 1 July 2019, the domain will become available to anyone who wants to register it.
Domain names ending in .co.uk, .org.uk, .me.uk, .ltd.uk, .plc.uk and .net.uk are eligible, subject to certain criteria. More information can be found here https://www.theukdomain.uk/uk-rights-faqs/
Need help – call Alchemy Systems on 0330 043 0801