Thanks guys, appreciate the replies. Grinding the rim is a new one on me, but I understand why it's done. I quite like the idea of my rims staying white and running a disc brake would allow that but I can't get out of my head that a disc on the back just won't quite do the job, and research on here is a mind field in terms of what disc brakes are worth using and what aren't. I'm going to run hydraulic brakes either way as I don't like cable brakes.
Peter_t - I'm from Hertfordshire but work in Norfolk during the week
Macca