To help other researchers who may also been interested in the Senior/Dodds/Grieveson families I am now going to post some marriage information which I have been able to find:
Mary Jane Grieveson and George Gill married at St Mary, Gateshead
22 December 1869
George's age was recorded as 22 - Mary Jane's age as 'Full'
Abode for both was 'Half Moon Lane'
Fathers:
John Gill - Gentleman
Robert Grieveson - Auctioneer
Four witnesses:
John Gill
Emma Senior (my ancestor!

(William?) (...ness?)
Edwin S (Frank?)
All signed
Margaret Dodds and Robert Grieveson married at St Ann, Newcastle upon Tyne
Entry 110
8 April 1850
Both 'Full Age'
Robert recorded as 'Railways Clark' (sic)
Fathers:
John Grieveson - Publican
Thomas Dodds - looks like 'Surgeon'. Staff member at Tyne and Wear Archives also agreed that this looks like 'Surgeon'
Witnesses:
Thomas Lloyd and (John?) Wheldon
All signed
By licence
I think Emma and Margaret Grieveson must have been cousins once removed. I think that Thomas Dodds must have been the brother of my bloodline ancestor Mary Dodds who married William Innis and whose daughter Mary married Edward Senior. This latter Mary was an only child according to a marriage notice I found for her and Edward.