Hi again Louise,
Here are Henrietta and George staying with what could be their grandparents?
1851 census:
HO107/2358, folio 339 page 7
Yorkshire, Balkholme
Isaac Hairsine, head, mar. 67, Farmer of 140 acres, employ 1 Lab,
b. Yorks. Asselby
Ann, wife, mar. 68, Yorks, South Cave
Ann, dau. unm. 26, b. Bellasize
Henrieta Simpson, visitor, 5, Scholar, b. Howden
George Simpson, visitor, 4, Scholar, b. Howden
Pels 
I have an Ann Hairsine who marries in to my family who I believe could be the Ann aged 26 above.
Ann gives her birthplace as Bellasize, although I have her as being born c.1829/30.
Marriage - George Slingsby UNDERWOOD to Ann HAIRSINE, May 12th 1852, Howden Parish Church.
Known children:
Emily Slingsby UNDERWOOD, born 1853 North Cave, died 1853
William Henry UNDERWOOD, born 1854 New Village
Tom George UNDERWOOD, born 1855 Wallingfen
Henrietta UNDERWOOD, born 1858 Wallingfen, died 1912 Newport (Henrietta married into another of my lines).
I haven't checked this out any further as they are not direct ancestors, but I thought I'd throw it into the mix in case it was relevant.

Jo.
Edit - Also possibly another Hairsine link. I have an Esther HAIRSINE who married Dinnis UNDERWOOD May 7th 1866 at Howden Minster. Dinnis and George Slingsby UNDERWOOD were brothers. Esther was born c.1823 in South Cave on census returns. Looking on IGI there is a baptism at Eastrington as follows:
Esther HAIRSINE, parents Isaac and Henrietta, bapt 18 May 1823, Eastrington, and also to same parents at Eastrington,
Ann HAIRSINE, bapt 20 December 1824
Margaret HAIRSINE, bapt 17 March 1817
Mary Ann HAIRSINE, bapt 25 February 1813
Henrietta HAIRSINE, bapt 23 April 1815
Isaac HAIRSINE, bapt 29 May 1819
Christiana HAIRSINE, bapt 2 April 1821
Rhoda HAIRSINE, bapt 4 May 1827
Emma HAIRSINE, bapt 22 August 1828