For completeness, for the potential bus users:
I don't know where in T5 that (BA1) goes from,
Bus stop 21 at T5. Out of the Terminal, cross the first bus lane and 21 is towards the southern (left hand) end of the next lane. It's "labelled", there's usually plenty of crew waiting for the car park bus and plenty of "suits" waiting for the shuttle to Waterside.
Words of warning -
1. BA 1 only runs weekdays.
2. The BA1 runs both clockwise and anticlockwise around LHR, check with the driver that he/she is going to Cranebank, otherwise you'll have detour of the cargo area, a very long journey....and see T5 twice!
http://www.baa.com/assets/Internet/H...Allocation.pdf
Good luck.