Same thing recently happened to Rachelcb80 on a red and white quilt she was putting in a show.
Here's her thread:
http://www.quiltingboard.com/t-144836-1.htm
Red bled all over the white (she hadn't prewashed).
Ah, you're in the UK - were you also using a front loading washer?
She fixed it - read the thread.
Just don't put it in the dryer yet.
Good luck!