While it is not uncommon in the winter here in the UK to have to cancel lessons in the early part of the day (including the DSA cancelling driving tests), the conditions on Feb 2nd 2009 meant at least almost 2 days of cancellation for instructors with the resultant loss in earnings which is even worsened by the current credit crunch, and weekly franchise fees are still due which means additional pressure on driving school owners.
Driving Test and Snow
The DSA will usually cancel a driving test if there is extreme weather conditions, Snow, black ice or other dangerous driving conditions, so it was not just instructors that were out of pocket in the recent snow storms, the driving standards agency doesn't usually give compensation for tests cancelled due to weather conditions, though you'll have to check with the local test centre, as this weeks instance might be a bit different since I don't think the examiners were actually able to get to work either!
If you have a test and are not sure if it will go ahead, the number to contact the driving test centre is on the appointment letter, don't call the DSA central booking office or Nottingham Hq, as they won't be able to help you.