Turns out it was my bowel that had become involved.
Just back from 5 night stay in Worcester Royal after a PR bleed and significant lower intestinal pain. It took me 2 days to get them to try the team providing my chemo in Coventry. I was shifted across 3 wards and 4 consultants before they decided to double my dose of pred and give me MST, which did the trick.
Alls well that ends well, but my general impression was you mention you have vasculitis and you immediately see a furrowed and worried brow!