If you order the marriage cert it will give you fathers' names and occupations, which will then take you back a generation. Also it will confirm Hannah's maiden name.
You mention a Thomas Bowland - in 1861 he was in Lambeth aged 29 born Sawtry - do you have details of this census as he may be connected with Henry - brother possibly? In fact in 1861 there are a number of other Bowlands living in Sawtry, so I'm surprised that I couldn't see any on 1841. They include William Bowland 73 farmer of 30 acres born Caistor Northants and Ann his wife 70 born Sawtry, who must be a possibility for being Henry's parents. (somewhat amusingly the indexer of 1861 has misread Sawtry Hunts so half a page of people have their birthplace as Sawley, Hungary!). They must be in Sawtry in 1841! I'll have another look, now I have some other christian names to look for....
Found them this time! (Poor quality image).
William Bowland 40 (43 scored through) farmer Not born in Hunts
Ann Bowland 40 (43 scored through) born in Hunts
Jane Bowland 20 born in Hunts
Henry Bowland 15 born in Hunts
William Bowland 14 born in Hunts
Harriet Bowland 12 born in Hunts
Thomas Bowland 9 born in Hunts
William and Ann's ages seem to be 10 years out between 1841 and 1861, so 1851 might possibly give you a better idea. (in 1861 there is also a 44 year old unmarried Ann Bowland in Sawtry so she is probably another daughter which would make the 1861 ages more realistic)
Having a quick look at the IGI shows two William Bowlands christened in Castor Northants, one in 1788 the other in 1789, with different parents, so either might be your William. As Hunts is not at all well covered on the IGI you would need to check the parish register (probably Sawtry which is where Ann is shown in 1861 as having been born) to find the marriage between William and Mary before 1817.
Regards
David
