I think I go along with the climate explainations but maybe we have the wrong variety of sycamore/maple tree too. I'm sure we would be making it if it was possible.

Hotspur, I have just looked it up in my dictionary (Chambers 20th Century English). Our sycamore is the great maple (Acer pseudo-platanus). Your sycamore is what we would call a Plane (Platanus).

Jon