Hi Heather,
What a woman Tilly must have been! I do hope you're able to make some progress finding her history.
This is the 1851 census information.
This pair living in Kingston upon Hull, Yorkshire.
John Dalling, Head, U, 21, Travelling Draper, b. Scotland.
Isabella Dalling, Sister, U, 23, Housekeeper, b. Scotland.
HO197/2363, folio 863, p 27.
Living in Nottingham St Mary, Nottinghamshire.
William Dalling, Head, M, 40, Cordwainer, b. Scotland.
Wife and children born in Nottingham.
HO107/2132, folio 116, p 22.
There’s another family with the children born in Scotland but the father was Irish.
Of course this only gives you Dallings born in Scotland who were living in England in 1851. If you post on the Scotland board someone with access to that census will be able to tell you how many Dallings there were in Scotland.
Mind you, don't ignore the Devon connection. Because of the seafaring tradition, some people from that area were great travellers.
Good luck
Monica