Thanks for the replies a few weeks ago to the question: When do you change your chain?
Sadly it seems I might be too late. I got a shiny new 10 speed shimano chain and fitted it yesterday. I also carefully took apart the crankset, rear mech and cassette and cleaned them, put it all back togther and dry lubed it (yep chain doesn't need it but drive will.)
I took it for a spin this morning and the chain was beautifully smooth, BUT when I moved up gears to the top two little rings, CHUNK, CHUNK, CHUNK. It started skipping on the 12T and 11T. These are my main 'pushing hard' rings and see lots of flat out use training for my upcoming sportives.
I guess I will clean the old chain and refit it to the cassette. They will work together fine for the summer but it may mean I have to change the lot in September. It is a long slow and expensive business keeping you bike on the road. I did get 6000km out of the last rebuild and will get more I guess. At least I have a the new chain and some time, back to ebay to save 'shimano 10 speed cassette' as a search.