Sorry, but you’re out of date on this. The Boundary Commission (whose job this is) is required to review the boundaries of Parliamentary constituencies every five years. Its latest recommendations, due for ratification in 2018, are radical, including the reduction in the total number of seats from 650 to 600. In England, all but 68 of the 533 constituencies will have some changes to their boundaries.
Appreciate the update. I obviously had some bad information.