In reply to anthonyh:
Hi Anthonyh,
Very rare occasions the roads are completely close in Scotland, however it will be virtually impossible to do any winter climbing in Scotland without a car unless you are staying in CIC hut or something like it, in which case you will be force to stay there even if the conditions aren't good, it happens often that you have good conditions in the east (ie. Cairngorms) and bad in the west (ie. Ben Nevis), even within a week.
Mobility and capacity of changing plans is main key if you want to succeed
in Scotland, so in my opinion you need a car.
Enterprise in Edinburgh has good offers if book in advance on-line and the airport bus drop you by the door in 15min from the airport, £6 return I think.
I hope this helps.
Victor