You donīt need your own GNSS.
My reading of this is that, in order to publish GPS/Galileo approaches the State needs to demonstrate some form of integrity control that it, itself, controls. Hence the EU has EGNOS, and of course more localised GLS approaches. If I have this right, once we leave the EU, the UK won't be able to offer EGNOS approaches because EGNOS is not under its control. I'd appreciate it if someone who knows the subject could confirm or deny my reading. I can't find anything specific in the Chicago Convention, PANS OPS etc. Or is it the case that the UK can legally publish approaches that piggy-back on the EU's EGNOS system?