Do you think your aunt might remember anything more about the Scot/the American/the sons?  The smallest snippet can be an important clue.
I'm really really hoping so! She and the rest of my family have actually MET the Americans, back in the 60s. Unfortunately at the moment all anyone seems to remember is a few first names, no surnames.  

 We got the photos out a few weeks ago to try and jog some memories but to no avail. 
Kath - I've ordered a couple of marriage certs so far, both which are definitely not the one I'm after. Can't find anything on scotlands people. Next two on my list are:
Ellen Elizabeth Waite 1906 Apr-May-Jun   Bath Avon, Somerset   
Ellen Elizabeth Waite 1909 Jul-Aug-Sep    Mutford  Suffolk  
Bagpuss - nope I don't even know if he was definitely American!
Incidentally, am I right in thinking that Ellen's father Thomas appears to be bigamously married in the 1901 census?
I'm very interested you should say that - what happened to Thomas has been driving me up the wall! I take it you mean this family:
Josie Waite 5  
Rose Waite 30  
Stanley Waite 9  
Thomas Waite 28  
living in Eckington, Worcestershire?
I've looked into this before and can't find a marriage for a Thomas Waite and Rose - nor can I find birth certs for  Stanley and Josie Waite. I wonder if they were illegitimate children of my Thomas or prehaps the children of somebody else? I know from my grandfather that Thomas walked out on his wife Edith, which is probably why she is back living at home with her parents on the 1901 census.
Obviously if someone could prove me wrong at least I could draw a line through that option!