There's not masses of parking at BP on the A3, might be better to meet in the B&Q carpark at Ladymead. http://www.streetmap.co.uk/newmap.srf?x=499509&y=150839&z=1&sv=ladymead&st=6&tl=Ladymead,+Guildford,+Surrey,+GU1&searchp=newsearch.srf&mapp=newmap.srf
Perfect for a showy cruise through Guildford as well.