Perhaps you could address this issue Ivan.
[Yes!. On average the UK might see up to 33 reported damaging tornadoes every year. Some years the total can be far lower or much higher than this. For example in 1982 there were 150 tornadoes.This may seem very low when compared to figures from the United States, however we must not forget that the USA is 39 times larger than the UK. Because of this difference in size, we must consider land area. It was recognized by the American Scientist Dr. Ted Fujita (who devised the F-Scale) that the UK has more tornadoes per unit area than any other country in the world. ]
http://www.severewx.co.uk/tnfaq.htm
Sure suprised me as well when I first saw this a few years ago.