Shirl,
Do you know, that's so blindingly obvious, I'm seriously embarrassed! For some reason we were all assuming that Mary moved to Yeovil after George's disappearance/demise, but it doesn't of course have to be that way at all.
In theory, if Mary was telling the truth that she was still married in 1861, then it can't be either of the 1854 or 1859 deaths. If Trish's new find [thanks!] is the right lady, then she was widowed in 1871, so an 1863 death remains a possibility. On the other hand, if they weren't actually living together in 1861 he could have been absolutely anywhere!
I suspect the family are going to have to plump for a death certificate if they want to prove that 1863 is the right one.
Cheers,
Brian