Thanks for the responses!

Good to hear that it's not likely to be an infected shunt. But I don't fancy the idea of the thing coming to the end of its life. Such a whimp, aren't I?

I think that it's adhesions. Which I don't think is life-threatening. But it's a real pain.

Anyway, I've now told my GP that I need to see a neurosurgoen and she's making me an appointment. He probably won't have the faintest, either, but let's see!