Thankyou all for your input.
The likelyhood of Hannah Maria being a Symes is very much a distinct possibility. I have yet to find the marriage.
John & Hannah had a daughter, Hannah Maria, born 1812, Broadwater, Sussex, she being my 3rd gr grandmother. Her marriage to Thomas John Grinyer in 1830, Brighton, Sussex, there were 11 children. The second, a son, was born 1833, named William Symes Grinyer. There are other "Symes" as christian names throughout the Grinyer lines.
Hannah's siblings, that I have found so far are;
Thomas Symes, 12 March 1805, Cranborne.
Harriet, bapt18 Oct 1806, Cranborne
John Edwin, 5 June 1810, Cranborne
Hannah Maria, bapt 23 Aug 1812, St Mary, Broadwater, Sussex
George French, bapt 19 Nov 1819, Cranborne