"...it's a useful bargaining position."
I think it is a bit more than that. In EU27, their position is that control of Galileo's PRS needs to be entirely within the EU and that it would take a treaty change to allow the UK to be involved as a non-EU state i.e. it will never happen. If the British military need to be certain of the PRS system, what the EU is suggesting is inadequate.
Anyway, the Galileo facilities at Swanwick, Falkland Islands, Ascension, etc. are to be moved (at some considerable cost to the EC - these are huge contract changes).
Interestingly, Britain will continue to be a member of the European Space Agency (which is not an EU organisation) and ESA happens to be the design authority for Galileo. ESA would not be averse to assisting the UK in building an alternative to Galileo.