Biz,
If you do go by train see this (pasted from the CAA site):
By Rail
On arrival at Gatwick Airport Rail Station, enter the South Terminal concourse and proceed ahead towards ‘WH Smith’.
Before reaching ‘WH Smith’, turn right past the ‘Information’ desk on your right and head towards ‘Costa Coffee’ at the far end of the concourse.
Go past ‘Costa Coffee’ on your right and head towards ‘Left Baggage’.
Immediately to the right of the ‘Left Baggage’ counter, follow the signs for ‘Local Buses- Southbound’ and pass through the set of grey double doors and down the stairs to ground level.
Exit out of the building down the steps to the left and follow the path directly ahead to the bus stop on the same side of the road.
Take the No. 10 bus - which runs every 10 minutes - or the 100 or 200 which run at approximately 20 minute intervals (all stop outside the BT offices in City Place - see timetables below). Travel on these are free of charge for staff and visitors to Aviation House. When you get off the bus go right towards the roundabout and follow the road on past this and to the right - keeping the "Beehive" building to your right. Take the next right-hand turn and you will see Aviation House in front of you.
See further info here:
http://www.caa.co.uk/default.aspx?ca...90&pageid=1450
See also this map:
http://www.caa.co.uk/docs/33/CAA_MAP_GATWICK.PDF
It's no hassle getting the train. You will not get certificate that day but the doctor will probably give you a verbal yes or no.
Good luck.
S