Bollocks
"What the UK government will be most upset about is that the fact it will be no longer be allowed access to the highly secure military-grade signal Public Regulated Service (PRS), a huge blow that will put the UK, and its military, far behind other Western nations when it comes to using the latest global technologies."
For some reason I keep using that title when articles on Galileo crop up. The UK and it's military will not be left behind anything. As apparently needs pointing out every time, the PRS is identical in function to the commercial service which is available to anyone regardless of whether they're in the EU or not. The only difference is that the PRS is guaranteed to keep operating during emergencies while the commercial service can be switched off. Unless the UK goes to war with the EU (and Brexit hasn't quite gone that far yet), there is no reason for the EU to disable the UK's access to the regular commercial signal. Obviously the military would prefer the extra guarantee, but in practical terms it's not actually going to make any difference.
The reality is simply that it's all about money. The UK wants the contracts for building the things. Importantly, failing to get the contracts now will likely mean losing a lot of companies and expertise to Europe and so failing to get more contracts (not just EU ones) in the future as well. The UK has done pretty well at building up our satellite industry, and there's been a lot of talk (which may or may not be considered realistic) about developing much more local space-related stuff including launch systems and even manned missions. Seeing a significant portion of that industry up roots and move somewhere else would be a serious blow to those ambitions.
So no, the UK government is certainly not "most upset" about losing access to the PRS signal, they don't give the slightest shit about it. It's just a handy thing to point at and shout about national security rather than admit it's actually about money and thinking that having our own rockets will make them look good.