Sorry to be the bearer of bad news Blondshania, but pumpkin pies do not exist here. If you live near London, you *might* be able find some Libbys Pumpkin Pie mix at Selfridges or Harrods.
And I think you can order it from some of the American online stores too.
Other than that though, you won't find any mention of such a thing here! Most Brits, unless they've spent some time in the US, haven't ever tried it, and aren't overly fond of the idea.
Good luck!