The boundary of the South East region (left) includes the Unitary Authority of Milton Keynes as well as the county of Buckinghamshire (right)
The county is in RU area 31, along with Berkshire and Oxfordshire.
https://en.wikipedia.org/wiki/List_of_Parliamentary_constituencies_in_Buckinghamshire (see below for embedded documents The first is the 2017 General election results and the one below it is the 2015 results)
2017 General election
2015 General election