So this morning was driving to work and twice had a very hard brake pedal and very unresponsive brakes! Wasn't an issue as very few people are awake that early on a Saturday but want to get to the bottom of it before the misses and little one use the car. Seen a few threads online about water in the master cylinder due to blocked plenum drains but last time I checked them they were all clear. Other thought was could it be to do with the fact it was -1 outside? Calipers sticking? Any ideas?