I have been offered a CBR600 (not sure what year but I think around 1997/8 for £450.

It is running fine but needs some tidying/polishing and a respray on the main fairings. Sure that more stuff to replace would become evident but don't think it would be anything major from looking the bike over.

Is it worth it as a project bike or would there not be a decent return:effort ratio?

I think you would be pushed to make much of a profit on it, but if you want a decent little scratcher that stands you at very little....

Yeah, didn't think there would be much in it. Was thinking of getting it as a winter tatting project for me and give it to Mrs 955i as her new bike in the spring.

So long as it's a runner then it's got to be worth a punt

Agree - if its just for your own interest it sounds like a bargain and ideal for winter.