M25 junction 8, take the A217 northbound, this goes through Tadworth and Cheam. It's dual carriageway most of the way, although long stretches have a 40mph speed limit. This leads to a major roundabout with lights (Rose Hill). Take the third exit (Mitcham A217), this is Bishopsford Road and the ground is a mile further on. Go through two sets of lights, the road dips, and the entrance is on the right opposite a petrol station.
Mitcham Station is on the Croydon Tramlink, which links to the rail network at Wimbledon (6 stops), Mitcham (1 Stop), Croydon West and East (20-25 mins), plus others further east. Imperial Fields is 5 mins walk. Turn left on the road bridge station exit and keep walking.
Morden station, on the Northern Line, is the nearest (about 20-25 mins) or buses 201, 118.
The 118 and 280 go past the ground, 201 gets as close as the tram station