edit 1: More here: Brexit 'will force Airbus work on Galileo out of UK' and now here: Brexit: UK wants £1bn back from EU if it is excluded from Galileo
edit 2: And now more here: UK rebuffed over Galileo sat-nav procurement
The following excerpt is from the BBC News article Galileo: UK plan to launch rival to EU sat-nav system:
Graham Turnock, chief executive of the UK Space Agency, said early feasibility work was under way into a UK system, which he said would cost a "lot less" than Galileo, thanks to work already done and "British know-how and ingenuity".
Asked by the BBC's Science Correspondent Jonathan Amos if it could be as much as £5bn, he said "tops".
And he warned that excluding the UK from Galileo could set the European programme back years and cost the EU billions more in development costs.
"We still think there is a 'win win' to be had here if the European Commission and the EU 27 change their minds.
"But at the moment they appear to be set on excluding the UK from industrial participation in the programme."
He said the UK had "a lot of the capability that would be needed for a sat-nav system because we developed them as part of our role in Galileo".
"We cannot launch yet, although obviously we are trying to address that, but this is something we think is in the realm of the credible," he added.
Question: How might excluding the UK from Galileo set the European programme back years and cost the EU billions?
What kinds of development would result in these costs? Are there basic technologies that have yet to be developed, or does this refer to some subsystem related to the GNSS payload or the spacecraft bus that a new supplier would have to start from scratch to (re)develop? Or something else?