At least two other ways!
I take it you obtained your information from a member submission on the IGI? IGI entries like this are a joke - if the member had really known anything about the marriage he would have included Elizabeth's maiden name, the date of the marriage, and the place. He didn't, so it's pure guesswork on his part, taken probably from the baptism of one of their children in Southoe, or from a census. He got the year and the place wrong!
The only marriage in Hunts at around this time of a William Garner was at Diddington, a mile north of Southoe, in 1810 with Elizabeth Pestel, per Hunts Marriage Index (another way number one). Also Diddington parish register - baptisms and marriages - has been extracted onto the BVRI (another way number two), where the marriage date is shown as 12 Oct 1810. Both were of the parish of Diddington. If you check the parish register microfilm (see below) you'll get the names of the witnesses which may give a clue.
I assume it is them living in Southoe in 1841 and 1851 - shout if you haven't got full details (the one's John found). The birthplace of William, age 61 in 1851, is given as Old Warden, Beds, where there's a baptism of a William Garner on 2 March 1789, son of Thomas and Mary Garner, labourer (parish register transcript, but also on the IGI as an extracted entry, so reliable, unlike the member submission above)
Elizabeth was age 58 in 1851, birthplace Southoe, where the register has been filmed by the LDS but is on neither the IGI nor the BVRI. You'll need to view the film at your nearest LDS Family History Centre - there is an Elizabeth Pestall baptised at Diddington on 12 Jan 1789, daughter of Thomas and Mary, but the place is at variance with censuses (notwithstanding that she married in Diddington) and the age is 3 years adrift, which is why I say you need to check the Southoe register
David
