Thanks for the reply Nigel,
I thought the reason for keeping the track wide was to reduce the resistance so I don't have to worry about this 50ohm's, then just connect a normal 50ohm GPS antenna
So it appears I still fon't understanf this, if I have a track 40mm long to a MMCX connector do I need to worry about it's resistance size / shape clearance or not? from what your saying Nigel, just make a thin track (2mm) with space around it then just again connect a normal 50ohm GPS antenna to it.