Well I finally got a reply from the Borthwick so I thought I'd round off this thread with the details for any future searcher.
These are the people mentioned -
Will of Thomas Oliver of Carlton, Rothwell, York, Farmer, written 24 Mar 1834, proved 7 Dec 1836
Son, John Oliver of Carlton, Farmer
Son, Thomas Oliver of Carlton, Farmer
Daughter, Ann, wife of John Pease of Pontefract, Cabinet Maker
Deceased Daughter, Mary, late wife of John Swann of Newcastle, Glass Maker
5 unnamed Grandchildren, children of above Mary
Daughter, Elizabeth, wife of David Johnson of Thorp, Farmer
Daughter, Easter, wife of Isaac Banks of Lofthouse, Innkeeper
Daughter, Hannah Oliver of Carlton
This is exactly what I was hoping for, Mary is my 4th great grandmother and this proves she was the daughter of Thomas Oliver of Carlton. On occasion wills can be a real goldmine, tying together generations like nothing else can.
Thanks again for your help.