'but a passenger who is trying to get compensation from Easy on the basis that before they dispatched him to the frozen north, they knew they probably were not going to get him back.'
No airline can ever give this assurance if the weather is a significant factor in the argument. The major issue was relating to wet runway conditions. Therefore at the time Mr and Mrs bloggs departed, unless the airline knew that the runway was going to be wet at the time of their arrival X hours/days later, that claim wont stand up. Some airlines took a blanket descision once they new there was a period of extended wet weather likely to affect operations and safety, others obviously took a tactical on the day approach. Had there been a dry period, then the sliping and skidding issues would have been greatly reduced if not non existent.
Regarding brakeing assesment I wonder what the implications are for those airfields which use the 'center pedal' technique for their assesments? But thats probably a good question to ask in a technical forum and not in this thread.