Did the leaves change colour before they started to fall? Mine is gradually turning dark red - very early. I can't say for certain, but we've had such strange weather patterns this year, it could just be down to that. They are very tough plants, aren't they - normally unaffected by the cold.

You haven't seen any signs of disease or aphids, have you?

Part of it is the weather happening now, and part of it is the weather that you had earlier this year. Unusually cold weather now, or an unusually great difference between day and night temperatures, will cause the leaves too start to turn early. Plants that have been under drought stress in the summer often also start to turn early. Old gardeners also take early color change as a sign that the following winter will be hard. I don't know how the plants would know, but I've seen it work often enough for me to take the theory seriously.

Oh, not again, Tug! Unfortunately, I've heard from different sources that we might be on course for a third bitter winter in a row. Batten down the hatches! :-(((

A different answer from me - the north east side gets less sun, therefore the soil doesn't dry out so quickly, could that be the case? If the leaves are simply falling, my money's on water shortage causing it.

I know, Spritz, I know!! We had a hard winter here, too, though we cant be in the same atmospheric circulation patterns! Still too early in our seasonal cycle to tell yet what it's going to be like here, but we have had a relatively cool summer, miserable as it felt to me. I've been blaming the volcanoes, and if I remember correctly, Iceland had another medium-large eruption this spring.
Bamboo, wasn't the wall with the problem north facing, which should get even less sun?

Yep, you're right - now I reread the question, I see its the north facing one, not the north east, which has a problem - that's what happens when you're doing two things at once - I had the news running about the riots at the same time as answering... sorry!