Thanks for sticking with me. It's turning out far more interesting than I'd originally thought. More information I've just found:
1871 census Abode: Scarborough
William Robinson b.1847 Fridaythorpe, Yorkshire
Elizabeth Robinson b. 1851 Lowestoft, Suffolk
Jas William Robinson b.1871 (1 month) Scarborough
1861 census - Abode Garton
William Robinson b.1844 Fridaythorpe, Yorkshire
servant.
1851 census Abode: Fridaythorpe, Yorkshire
Thomas Robinson b.1824
Ann Robinson b.1825
Elizabeth Robinson b.1845
William Robinson b.1847
Sarah Robinson b.1849
James Robinson b.1851 (7 months)
So I'm happy that I have found William parents. Its interesting that William calls his children after his siblings.
In the 1871 census he and Elizabeth are with newborn son transcribed as Jas. I think its Jms (James) - this information is supported on the GRO registry.
So, to recap William (head) with:-
Wife 1 - Elizabeth Scarll - Children: James 1871, Mary Ann 1874 & Sarah 1876 - living Scarborough
Woman 2 - Eliza Saunders - Children: John George 1875 (illegimate, may not be Williams'), William 1876, Annie Bean 1877, Thomas 1880, Mary Jane 1883, James 1888, Bertie 1890 and Florence 1894 - living Kelsall, Cheshire
Wife 2 - Mary Gleave - married Delamere 1900.
Only bit I'm uncertain is whether he actually married Eliza Saunders and whether he got divorced before he married Mary Gleave. An Ancestry tree on Elizabeth Scarll states she died 1928 Scarborough, and as you say she is listed as married on the 1881 and 1891 census, with the 3 children.