The annoying thing, of course, is that it's not a simple repair job so I can see myself going to the shop. Which means at least one more day without the trusty steed. Bother. Bother. Bother.
I tried to take a picture of the offending bit but it didn't come out well. Here's one from the net which I think shows it. It's essentially the spring which keeps the pads from being forced on to your wheel all the time:
and here's the blurry broken bit from mine:
I suspect you may now have heard enough about springs to satisfy you for the day. KC