Andover I think
Yes, Nick ... it is indeed Andover.
If I need to travel into London / South Bank, if I'm travelling up early in the morning (before the car park at Andover gets full), if I've not got anyone else to pay for me, and if I need flexibility for my return home (a "I haven't a clue how long it will take" job), then Andover is my best park and ride option from Melksham.