These directions are taken from their website.
Take M4 to Reading Junction 11; turn right heading initially towards Basingstoke (A33). At second roundabout (end of dual carriageway) turn left; right at next roundabout; left at next one and follow signs into Hartley Wintney (B3011). At Hartley Wintney turn left and then right at roundabout and carry on into Fleet (A323) (going straight over roundabout just after railway bridge). Straight over the large cross-roads (traffic lights) and continue into Church Crookham (B3013). Straight over roundabout (Tweseldown Service Station on left) and after about 100 yards turn left into Bourley Road (The Tweseldown Pub on corner) - you are then at Tweseldown.
Take M3 to Junction 5 (Hook). Turn right heading towards Farnham (A287). Second left at roundabout (still Farnham) and second left again at next one (still towards Farnham). Keep going along the A287 (along long straight and then up long, long hill) until you reach another roundabout; turn left (B3013) down long hill until you enter Church Crookham. First right (The Tweseldown Pub ) into Bourley Road.
Take the A31 Hogs Back to Farnham (Shepherd & Flock roundabout). Take the A287 and then the A325 to Farnborough. You go straight through a couple of traffic lights in Hale and continue on until you come to the Wellington roundabout at the entrance to Aldershot. Take the first exit (signed Tweseldown) and travel along that road (military), through the woods, round the bends until you're almost at the end and you will be at Tweseldown.
Take the M3 south to Junction 4 then A331 to Farnborough. From there take A3011, turn left onto A325 towards Farnham. At Wellington roundabout (Aldershot - Tescos on left) turn right (signed Tweseldown) and follow military road almost to the end.
From the South
Take the M3 north to Junction 5 (Hook) and take first exit from motorway roundabout and then follow directions as from that point on the Basingstoke directions.