Thanks for that - and sorry I haven't replied sooner - I've been on holiday. I think you're right about the 1861 census - everything else fits, apart from William's name. John hasn't disappeared - he's on the following page, but was missed off the transcription! As John is my direct relative, it's quite important to me that he doesn't disappear too soon!

The info about the possible marriage between Isabella and William in 1855 is interesting - another avenue to explore. I have a slight concern that he's listed as 'James William', rather than 'William' as in the census, but his first child with Mary was called James, so it's a definite possible.

thanks again
muddy