As far as I remember.....
There are no cars allowed at the arrivals section of Terminal 1 which is on the ground floor (British style). The departures upstairs on the first floor, by road, through the tunnel, keep in the left lane and straight up the ramp, has limited drop off only. There used to be valet parking there. You could go upstairs to departures and take a chance of liasing with your pick up. Personally I'd send him a tenner. £4.50 for an hour's parking Terminal 1 Short Term and £15.50 for two disgusting cups of coffee and a flatulent croissant while they wait for yoiu.