As far as I'm aware, the UK channel didn't use any WeatherStar technology.
Actually, I believe they did. I think they may have used the 4000 in the past. I can be wrong (Since I am not even in the UK), but I saw somewhere talking about it. Google it... maybe you'd find something

I do know they did the same thing as "The Weather Channel - Latin America". TWC headquarters closed the UK TWC because it lacked viewers. They ran the 4000... if I am correct, unlike the Latin America TWC that used the modified XL unit. If I can recall, TWC UK ran form 1996-1998, and Latin America ran until 2002/2003. (Please excuse my bad organization in that...)