Re: UK has the resources
"Nobody will give a single fuck about yet another GNSS."
Exactly. Every smartphone will have support for three or four of GPS, GLONASS, Galileo, and Beidou-2.
That means billions of commodity receiver chips for those four... the UK system will depend on special UK only chips that are use nowhere else... nor by 99.9 percent of the UK population.
A contest between 'cheap as chips, works with everything you need' and 'almost hand carved, massively expensive, and quite possibly buggy'.