Originally Posted by
CD747
T5 long stay parking.
On your return, take the bus to T3 Business Parking and then walk across to T5 Long Stay immediately next door.
I'd second this approach, did it a few weeks back (BA out to BRU, SN back). Less than 10 minutes from parking up in T5 Long Stay to arriving at Terminal 5 and similar amount of time from Terminal 3 back to my car.