Yes the known jamming area is called the United Kingdom which they are allowed to jam at any time without NOTAM. There are airborne jammers as well for the war games. Around any of the Mil ranges though out the UK they can and do Jam. Recently they had it brought up in Parliment to get them to stop jamming during a war game because all the fishing boats were getting lost and with the current restrictions it meant that they were looking at not finding there fishing spots on the few days a month they could actually fish.
This isn't just one aircraft its happened in getting on for 36 airframes in my log book. And they are all public transport CofA's.
They will be approached approved but as there are very few GPS approaches in europe I haven't done one in anger. I did submit a form or two for the test ones in the UK but unfortuantely it didn't aid the cause because RAIM dropped and we converted to a visual without getting to the FAF but that could have been the FRA Hawker that was operating in the area for an exercise.
The only warning that comes up on the units is a very small flashing msg light and when you go press it twice it comes up RAIM fail, check your position or something like that. Most folk ignore it because it goes on and off at various points and usually goes away after a few mins.
But I have every expectation that all my experences will be put down to crap aircraft, crap equipment, crap pilots(even though we don't need a GPS to get where we are going). That its no fault of the GPS system and I should get out of the dark ages and put my faith in it when scraping my arse to the deck in 600m and OVC 001.
Peter we have no warnings whats so ever on the primary instruments when it fails.