BS,
I am not sure you think like a local NHS manager (fortunately).
Helipad = largely unused space : Car Park = Source of Revenue
You can even take it further than that (if you are a tiny bit cynical):
What do helicopters bring to hospitals? - Very sick people who spend a long time occupying beds and operating theatres. Who knows how the screwy pricing system works in the NHS. There could easily be an incentive to move such patients on......