There are some family trees on you know what for this family, with info that is worth checking. I know you can't trust other peoples research because it can be rubbish, but it sometimes points you in the right direction.
One tree has a death date for Margaret Noble of 18 Jan 1856 which you could check from the cert you have. Same tree has a death date for Elizabeth (Betsy) Middlemiss/Noble of 3 Sep 1863 at Shidlaw, Carham. That would tie in nicely with the death cert you have ordered, if correct.
Same tree has the marriage of Andrew Middlemiss and Elizabeth Noble at Coldstream, 5 Jul 1839. No such marriage on Scotlands People, but it could have been an Irregular Marriage at Coldstream Bridge where people on both sides of the border often went to marry in a hurry. Some kind person on here may be able to do a look up, although not all records exist, or ask the Tree owner where they got their info from.
Another tack for George would be to get a copy of his marriage cert from Scotlands People, see who he says his parents are (I know it gets expensive). In 1901 this could be him.
Blackadder Lodge N, Edrom, Berwickshire,
George Middlemas, 36, Forester (wood), b. Northumberland,
Jane Middlemas, wife 26, b. Ancrum, Roxburghshire,
Maggie Middlemas, dau, 2, b. Edrom, Berwickshire,
Scotlands People has a marriage of a George Middle* and Jane in 1896.
He might be on the 1911 on Scotlands People as well, not sure if there is any additional info on the Scottish 1911 vs English 1911.
Alan.