Thanks for the reply keithy. I was considering getting out the masking tape and spraying in situ but the thought of it going wrong and ending up looking worse is putting me off. I think a thoroughly good clean up is possibly the best solution. It was the effort vs result that caused this post so I could get a few other opinions.

I've had quite few bikes, mostly jap and never seen this much corrosion in such a short space of time, I even had a harley that faired better but only just.