Noodley is correct in thinking there is a night porter at the Fife Arms.
A friend and I once knocked him up in the very wee hours at the end of a Snow Roads permanent.
(He was actually vacuuming the lobby; the porter that is, not Noodley or my friend)
the Youth Hostel ? (depends on times I suppose)
Craig suggested link.co.uk.
link ATM web locator edit: original link directly to Braemar ATMs from link.co.uk has expired so it's been removed.
If you fail to find anything in Braemar and depending on your direction, there is Blairgowrie or Ballater. There's not much in the way of a shortcut
so missing Braemar shouldn't, IMO, be a problem. If that's the case, a note to Lorraine submitted with your brevet would be acceptable.