Andy we've got a cobnut tree in our hedgerow and it grows really well, we've got a clay soil. We were looking at nut trees recently as we've got a gap in the hedgerow that we wanted to fill, but decided against using a nut because the gap is not really big enough and not enough sun for a nut tree. Have a look at
www.kenmuir.co.uk, there are some nut varieties available there which might give you an idea what can be grown in UK, I'm pretty sure they had Sweet Almond among others.
