Thank you Liz for your time and help.
To be honest not knowing the Isle of Man I have no idea how big a search for William Henry Cox would be. Basically I need to know the earliest that he can be found in voters books anywhere on the island, to find out when he is first recorded on the Isle of Man, (it would be from 1891) if you can help with this at all, however small it would be much appreciated. You have searched the Douglas ones from 1900 to 1906 with no trace so perhaps he was lurking on another part of the island! The entry from 1899 Union Mills is most interesting to me, as you say there was another name, would you be able to check this one out for me to see what the middle name was and also the ?? bit after the name Cox, that you mention.
Thank you again.
Ewan