Yes, rosie99, I ordered up the certificate for Thomas and he is down as a Porter on this. I also had some help about 10 years ago with someone who looked up christenings and burials in St Martins in Birmingham. The occupation is consistently that of a Porter and they are living in the Deritend/Digbeth area of Birmingham city centre.
Thanks claire for having a look at FindmyPast. Sad that there aren't any more clues to be had from this marriage record. Nevermind.
I have just sent off for a death certificate for a WILLIAM JENKINS from 1849 who was living at Great Colmore Street. The age fits and this would have been after the birth of their last child and before Elizabeth became a widow on the 1851 census. I'm not sure whether this will give any other information of use but thought it worth a last punt!
Thanks, as always, to the helpful Rootschat community