Hi seasby
Do you have a copy of Thomas' birth certificate?
Births Dec 1885
Pope Thomas Harry O Stourbridge 6c 175
If his name is Oliff it tends to support the fact that there is a connection to the Marylebone Popes since they too had Oliff as a middle name, as evidenced by Amy's middle name. There is also the photographic connection. Having a copy of the marriage certificate would also help prove it was this Thomas the son of a Thomas.
It doesn't however prove that Thomas Pope was the father of the subsequent children and your Sarah. If you are living in Wollaston what you tell the registrar in more distant Stourbridge when you register the child and what is strictly the truth are two different things. There were no checks in the system and if you walked in with a wedding ring on your finger and claimed the child was the legitimate child of your marriage the registrar was not going to question it. The 1891 census gives Thomas a long way from Wollaston, if he ever went there, and also with a status of single indicating he had left the marriage (divorce would be an expensive process and beyond ordinary peoples' means at the time) which may only lasted the time it took Ellen to become pregnant and marry when working away from home. She may have returned to Wollaston to give birth to Thomas Harry O without a husband if the marriage failed very quickly.
While what is said to a registrar in further away Stourbridge can be bluffed out, what is said to the local vicar in the parish you are living in isn't so easy since baptisms will take place in the local church in front of your friends and neighbours. Have you checked church baptisms to see if the children were baptised? I believe Old Swinford is the parish covering Wollaston.
http://www.genuki.org.uk/big/eng/WOR/Oldswinford/index.html#ChurchRecordsThe IGI coverage of the baptisms ceases in 1877.
Regards
Valda