Rob, i used to live in Newcastle and bought an 82 CR125 new back in the day.
one of my favourite bikes of all time. i loved it, it did everything i threw at it and just kept on delivering.
if you do decide to fix it up for a racer though, bear in mind it being an 82 model will slot into the pre~85 category and it will be a little outclassed by the later 83,84 models.
but if it's just about fun, then they're cool bikes for sure.
and i'm pretty sure Mainline doesn't know what he's talking about