Flashing blade,dont know what enquiries you have made about your mountaineering course, or if you,ve chosen one, but they usually come as residential.Maybe a word with the organisers of the course and they might let you park in the grounds of wherever you stay?.
In relation to the Fort William area the road into Glen Nevis used to have plenty of stopping spots however the estate has put up "no overnighting" signs.The Glen would be quiet at this time of the year.If you go down the Glen and if you have a small low van less than 7 ft wide you would be able to drive down past the big car park at the bottom,passed Polldubh crags and continue to the road end where there is a further car parking area at which you could stay.
There is a new car park sign posted "The North face car park"which is about a mile outside Fort William on the road towards Spean Bridge which gives access to the Ben Nevis north face which might be a spot.I havent visited this one yet.
In relation to the surrounding area Spean Bridge,Glenfinnan,Glencoe once you know where you would be based more spots would be open to you.