Hi
I have a record of the burial of Ann Tomlin, 9th Feb 1847 at St John Boxmoor, aged 45, I think she is most probably your Ann, in which case that gives us a birth date of c1802. From Family Search IGI there is a marriage for James Tomlin & Ann Golding, 23rd Dec 1826 St Michael St Albans & a birth for Ann Golding 13th March 1802 in Hemel Hempstead, parent Samuel & Sarah, could be a possible first marriage.
From Free BMD there is a marriage for James Tomlin to Eliza Turney June qtr 1848 Vol 6 Page 677 & also a possible death for Eliza Tomlin Mar qtr 1857 Vol 3a page 202 both Hemel Hempstead.
I see from the 1861 where James is now with Mary apart from his own children there are also Mary's children named How. Free BMD has the marriage of Mary How to James Tomlin June qtr 1857 Vol 3a page 404 Hemel Hempstead, I checked the 1851 & found Mary married to Ezekiel How, Ezekiel died Sep qtr 1855 vol 3a page 177 Hemel Hempstead. Purely by chance I found on Family Search IGI the birth of Mary & Ezekiel's daughter Angelina born 1853 & her mother is named as Mary Pettifer which falls in nicely with the marriage from Free BMD for Ezekiel How Sep qtr 1841 vol 6 page 703 Hemel Hempstead, other name on page is Mary Ann Pettifer.
Also from the IGI there is a James Tomlin born 30th Sept 1808, christened 23rd Oct 1808 Hemel Hempstead, parents John Tomlin & Charlotte.
Hope this hasn't confused you to much & has helped a little.

Maddie