I just noticed an interesting AIC: NOTIFICATION OF GPS JAMMING EXERCISE – HEBRIDES RANGES DURING PERIOD 21 JULY - 1 AUGUST 2014.
The Ministry of Defence is planning a GPS jamming exercise:
Jamming will occur across the 24 MHz bands centred around 1227.60 MHz and 1575.42 MHz. A Falcon 20 aircraft will be equipped with 2 high power jamming pods (1kw), one for each GPS frequency.
What effect would this have on a plane entering the jammed airspace?