GPS disruption is NOTAM'd or scheduled with Ofcom[1] from time-to-time, although not usually at the airport itself. Given that Gatwick was shut at the time, it wouldn't have affected the aircraft since they weren't able to go anywhere.

[1] https://www.ofcom.org.uk/spectrum/information/gps-jamming-ex...

Which is fine because it’s not necessary for aviation.

I wonder how much of a problem that would actually cause? Surely they could announce the lack of GPS on ATC and the pilots could revert to ground based navaids. Of course it might be difficult to keep the effect localised considering how weak the competing signal from space is.