I don't know the postcode, but here's a close up Map showing the A339 - you need to turn off this on to Galley lane (see map)
On this pic, Basingstoke is south, and Newbury is north.
Which direction are you coming from? I can give you detailed directions if you need but it will be sign posted from Galley lane and it's really quite simple
Edited - may as well put directions!
From Newbury:
Head on the A339 towards Basingstoke, stay on this road and you will enter Headley village (signposted). You'll go past a Restaurant called Amara on the left, then shortly after that is Headey Tyres, Headley bodyshop and Scott's Cars (all on the left). Galley lane is just after these on the Left.
From Basingstoke:
You will go through a village called Kingsclere, but keep heading straight on the A339, you will pass the "Star Inn" on your left, the Road sweeps round to the right and goes straight. Continue on this road and you will get to Cheam School on your left, Galley Lane is shortly after on your Right hand side.
Hope that helps but please PM me if you're unclear at all.
Thanks,