Mostly you don't get any no-claims and you need to start from scratch, but some specialist policies will apply an existing NCD onto a policy (but not let the policy accrue any in it's own right). I did read about a large mainstream insurer who did this too, but I can't remember who there were now... Pistonheads might have something about it.

PH might be a place to ask/search for alloy refurbishers too - it's quite a common problem.