Hi Elizabeth ,
May have found something for you , 1851 Census Egremont , Cumberland , England
William Thompson 56 Papermaker Scotland , Fife
Margaret Thompson 53 Scotland , Galloway
Margaret Thompson 20 Dressmaker ,Isle of Man
James Thompson 18 , Blacksmith, Lancashire , Bolton
Jane Thompson 13 , Scholar , Isle of Man.

This lead to :

Christened Margaret Thompson, 14/7/1830 Braddan IOM , F William M Margaret Halliday

Birth James Thompson 15/7/1832 Farnworth, Bolton , Lancs F William M Margaret Huliday

Christened John Thompson 19/8/1821 Tongland , Kirkcudbright, Sco, F William M Margaret Halliday.

Christened 4/1/1820 William Thompson, Tongland F William M Margaret Halliday

Christened 22/11/1834 Sarah Thompson, Rerrick, Kirkcudbright.

Possible birth for Agnes
Agnes Thompson , ch 23/12/1816 , Wigtown, Wigtownshire, Sco.

This is based on Wigtown being a book town - paper ?? and Rerrick, Wigtown, Tongland all close/part of (depending on what you read) to where mother Margaret was born - County Galloway.

I have never in all my research ever found a family who moved around so much , seems every two years they moved between Scotland, England and the Isle of Man

Cheers
David Dwyer