On another note - its worth considering the potential that your GPS is not going to work...
Q) EGTT/QWELW/IV/BO/W/000/400/5112N00158W065
B) FROM: 12/05/07 07:00C) TO: 12/05/11 20:00
E) GPS JAMMING EXER. JAMMER BASED WI 8NM RADIUS OF 5112N 00158W(SALISBURY PLAIN, WILTSHIRE). COVERAGE WI 15NM RADIUS AND ARC 355AND 050 DEG TRUE UP TO MAX RANGE 65NM AND 40000FT AMSL. AIC P046/2012REFERS. OPS CTC 01980674xxx OR 07776482xxx. 12-05-0067/AS 2.LOWER: SFC
UPPER: 40000FT AMSL
SCHEDULE: 0700-2000
DO NOT ASSUME that Sky Demon is going to be able to warn you of the RA(T) areas with reliability