This has been discussed before, but there is a "GP6 vertical" at 53°30'02"N 0°00'14"E, which has been marked incorrectly, I can say with 99% confidence, that's a Mechtric MS22. They are manufactured in my country, Australia, and are found all over the country.
Now, you may be going "oh but every MS22 is blue, this one is white!"
Well, the first generation MS22 which began production in around 2002/3, was white, and looks almost identical to the siren marked above.