GPS coverage is regularly tinkered with, particularly during annaul naval war games, and it rarely affects domestic users.
Galileo looks great on paper, but the reality is that the block 1 GPS satellites from the 1970s were more reliable than the so called state of the art Galileo birds of today.
Galileo is as pointless as the come. The extra resolution (which theyre having trouble delivering anyway) is of little practical use to non military consumers.
Also the idea of an independent system in the event of war is pointless as most major adversaries, the US, Russia, and even the UK, have anti satellite weapons, something which the EU themselves do not have - in the event of a big shooting war Galileo will very quickly be swatted aside leaving the EU reliant upon a system that has suddenly ceased to exist, and they have no counter-strike ability of their own.
In reality, the EU will always be reliant upon GPS for military use because Galileo is so shockingly unreliable anyway. They'll just never admit it.