Elizabeth/Elisabeth Sheffield born approx 1792 and died 13 August 1862 in Newport Pagnell, married a John Tandy (1789-1890) in Sherington in December 1811.
In October 1811, also in Sherington - a Thomas Sheffield (possibly born about 1791) married an Elizabeth Pilgrim.
The Milton Keynes Heritage Association (MKHA) website
http://www.mkheritage.co.uk/ has links to historical societies in a number of the villages in the area where they have transcribed records and I looked for Sheffields or Tandys on the Sherington site.
This tells me that John Tandy of Newport Pagnell married Elisabeth Sheffield 10
Dec. 1811, the witnesses being Phillip Tandy and Edward Caporn, and Thomas Sheffield married Elizabeth Pilgrim 14 Oct.1811, the witnesses being Matthew Winnright and Mary Joyce. Both marriages were by banns.
An Elizabeth Sheffield aged 24 was buried at Sherington 17th November 1815, which looks like it is probably Thomas' wife.
There don't appear to be any other Sheffield events in Sherington in the period the data covers which suggests the Sheffields weren't local to the village.
There used to be a shop in Newport "A. Tandy - Tailor" - it would be worth looking at the Newport Pagnell Historical Society pages from the MKHA website and contacting them to see if they can tell you anything about John Tandy and his wife Elisabeth (nee Sheffield).
Before the building of the by-pass Sherington (now a quiet backwater of Milton Keynes) was on the road from Newport through Emberton and Olney to Wellingborough, a busy route.
The railway came to both Olney and Newport - two different lines - but this is after we have these Sheffields marrying in Sherington.