RAIM is baro-aiding and works (in general) only if you are receiving only (IIRC) 3 satellites. If you are receiving "loads" then it doesn't do anything.
If they jam GPS then London will be jammed with lost drivers... that really will be fun.
One should not equate a lack of "gadget proficiency" with the use of GPS. You can suffer from the former with any piece of nontrivial avionics, if you don't read the manual and/or try to do something odd during the flight.