Simon,
I have had a look at your query and done what I can online. I dont live in Sussex so I cant do personal look ups there for you, perhaps someone who lives there can help. There is limited 'SussexOPC' evidence,' Hugh Wallis batches' info (IGI batches)but with a little detective work I have got this:-
Your William is not quite sure where he was born. The censuses give us this:
1841 at Mayfield. In Hendey household age 15yrs (rounded) with sister July (Julia ?) 10yrs. Both born in Sussex
1851 not found
1861 at Falmer. Age 32, wife Ann 28 He says he comes from Waldron, she is from Chiddingly. He is an Ag. labr.
children Caroline, Jabez, George and Jane
******IGI William Sands married Ann Pomphrey 30/3/1851 at St Clements Hastings. Ask to view the church register which may name the parents and witnesses. A kindly vicar may photograph the register and E Mail you a JPEG! or send for the marriage certificate to the registry office at Hastings.
Clearly the couple were in the Hastings area in the early 1850's
1871 The family are at Folkington, Sx. William is 40yrs, Ann 37. He is a farm bailiff.
Children George, Jane, George and Frank
1881 The family are at Beddingham Sussex. He is now a widower. He is an Ag lab
children Caroline, John William and Frank
1891 They are at Selmeston. Greenhouse farm. He is a farm foreman. Wllm. is 61yrs
He is with single dau. Caroline 47yrs and a boarder Wm Gower 20yrs.
1901 They are at Berwick Sx. William Sands 70yrs. Dau caroline 47yrs. Described as an ordinary agri. wkr.
grandson Harold F. Sands 10yrs living with them. Says he is from Framfield in Sussex.
The parentage. Where do you get his father's name as being 'Henry'. I cant find a reference to this.
He is not the son of Thomas and Hannah (nee Chewter) of Mayfield. They had a William born in 1829 but that child died an infant.
I dont really have any ideas, Ive checked the IGI. The waldron register might offer you hope but the best chance might be the marriage certificate, that looks to be the right one. Best of luck , like to hear if you can solve this
M.Ann