After the engine work the CBF fired up and ran ok. I think the little bike has a bit of life left in it.
The CBF was a pleasure to work on. It's well made, access is good and things came apart and went back together without any problems.
Was it worth it? The cost of the parts was fairly small - £115. I spent some time doing the work but, hey, it's a hobby and time isn't an issue for a "man of leisure". Most people would have scrapped the bike after such an incident. This is understandable. But if I get another couple of years out of the bike it will have been worthwhile.