Civil servants are confused
… Examples of other top level domains include .com, .co.uk, .net or .org."
.co.uk is a second-level domain not a TLD. They also might have suggested 2nd level domains of our ccTLD to UK domain holders such as .org.uk as being more appropriate.
Anyway, pleased to see the government evidently know what they're doing and I feel sure Brexit is going to be a remarkable success....which of course is absolutely nothing to do with why I'm leaving the country.