Gus,
If you come on the M8 at Hermiston Gait, go past the Newbridge cut off then take the next one at Livingston.
On the slip road, go to the roundabout at the end, keep to the right as the road on the left merges away to miss he roundabout.
The BP Services are right ahead of you - can't miss them, 2nd exit on the roundabout with a Premier Travel Inn on it's right hand side.
I'll PM you my mobile number.