Hi
I am not sure but there may be something wrong with the indexing.
I have checked various sites, there is an Emily Bentley coming up for 1859 Newark Nottinghamshire, 7b 511, Q2 but no spouse shown. I went on Free BMD and put in the reference 1859, 7b 511 and William Combes did come up but as being married in Newent. Information given about this was that for Newent registration district a reference of 6a would have been expected and not 7b as this was not a valid ref for Newent.
I can only suggest two things, either get in touch with the local registry office and ask them to check whether the Emily Bentley has a spouse William Combes before purchase or get one of the children's birth certificates to see what Emily's maiden name was.
evie