I'm also researching Joseph HAMSTEAD and Ann MORRIS / MORRIES and like you, am stuck at this point but I have no evidence of their temporary change of name.    Did you get any further?   Can we swap any notes so far?
All I've got is:
1861 CENSUS [Rotherham, S. Yorkshire]
Joseph HAMSTEAD FAMILY:   38, Orchard Yard, Rotherham [Folio R9/3506/F?]
Joseph: Head 32y Labourer at Iron Works. b.1829, Philley, Cornwall 
Ann        : Wife 30   b.1831, Ireland
Elizabeth  Dau    9   b.1852 Ashton Under Lyne, Lancs
Peter        Son    8   b.1853 Ashton Under Lyne, Lancs
Mary         Dau    6   b.1855 Ashton Under Lyne, Lancs
Ann          Dau    4   b.1857 Rotherham, Yorkshire
Thomas    Son  10m  b.1860 Rotherham, Yorkshire
Ann KELLEY    17  Boarder. works at factory. b. 1844 Ireland
Trevor