In reply to Sean Kelly:
> There's a car park on the west side of the A9 near the old railway halt. Also a b&b nearby which I used a couple of years back is ok.
Do you mean Balsporran Cottages: https://www.google.co.uk/maps/@56.883466,-4.253731,199m/data=!3m1!1e3?
I can thoroughly recommend the B&B there, especially if you're in to carpentry and woodwork, that being the second interest/business of mein host. He's also generous with a welcome dram when you first arrive. It is certainly a good location from which to access Beinn Udlamain and the rest of the Drumochter Hills west of the A9 (which can easily be done in one day).
AFAIK there never was a halt there. The nearest station on the line that is no longer extant was at Dalnaspidal Lodge, about 4 miles further south on the other side of the pass. (Dalwhinnie station, which is still open, is about the same distance further north.)
EDIT: I now realise that you were suggesting parking at Dalnaspidal, which of course would also work for accessing the hills.
Post edited at 15:10