Hi John
Not a lot, but maybe a couple of pointers..
The marriage looks good.
IGI:
5 May 1746 James Graham & Mary Mirehouse, All Saints, Cockermouth, mar.
Possible baptisms, Mary:
21 Dec 1711 Mary d. of Jno. Mirehouse, Lowswater, bap.
4 Jan 1724 Mary d. of Jno. Mirehouse, Lowswater, bap.
11 Mar 1704 Mary d. of John Myrehouse, Lorton, bap.
26 Feb 1722 Mary d. of Jonathan Mirehouse, Dean, bap.
Have you any info on their offspring? There is an unsourced Anc, Tree suggesting they had at least 2 sons, George b. 1767 and John b. 1770, quite a gap from 1746
The Mary bap. 1711 looks to be person of 'high standing' (though they could still be related). Link >
http://histfam.familysearch.org/getperson.php?personID=I104356&tree=Nixon
It doesn't look as though she married, unless I've overlooked it.
Geoff