OK, thanks!!!
I can see Margaret with her family in 1841.
In 1851 I can see a Margaret as a Servant, of the right age, in Trawscoed, Upper Llanidloes. Birthplace is shown as Carno, Montgomeryshire. I don't think this is the right one??? Have you got the full reference for the 1851 please?
In 1861 she is with another Astley family (her brother Jeremiah is there also), but where is her son Thomas??? He would be about 3 years old.
Ah!!! I have just answered my own question

Here he is in 1861 with his grandparents:-
RG9/4247 Folio 54 Page 8
Bronhaul, Esgob & Castle, MontgomeryshireEvan Astley Head Mar 54 Ag Lab born Montgomeryshire Penegoes
Martha Astley Wife Mar 46 born Montgomeryshire Llandinam
John Astley Son 13 Farmers Boy born Montgomeryshire Carno
Elizabeth Astley Dau 11 Scholar born Montgomeryshire Carno
Ann Astley Dau 9 born Montgomeryshire Llanwnog
Richard Astley Son 7 born Montgomeryshire Llanwnog
Martha Astley Dau 5 born Montgomeryshire Llanwnog
Susan Astley Dau 4 born Montgomeryshire Llanwnog
Sarah Astley Dau 1 born Montgomeryshire Llanwnog
Thomas Astley Grandson 2 born Montgomeryshire Llanwnog
Have you got your GG Grandfather's birth certificate?
Jan