We think that with all the renovations that we've been doing, someone has turned off the power for some reason at the mains, turned it back on again but not reset the pre-set times for the heating to come on. Ultimately leading to the pipes freezing and cracking leading up to the cold water tank.
Feeling slighly better about it now, need to replace floorboards etc but it's not as bad as I thought!
Well I'm glad for you that it's not as bad as you first thought. That's a consolation. Just sucks that it had to happen at all.