Brake fluid leak

I have got a leak in the brake fluid from somewhere. It has started recently (last couple of days), and I wonder whether it is related to driving the car over some hard, compacted ice. Because the car is always wet it is difficult to see exactly where it is coming from. Are there any areas I should be looking at first? I was thinking that it could have been a brake line where it goes into the calipers as this seems to be the most vulnerable to any damage?

Typical that it happens the day before Christmas Eve!

Merry Christmas everyone!

Jon