These do not like to dry out completely, although they prefer well drained soil, and the area around a tree will be quite dry. It'll have been fine earlier in the year with all the frequent rain, but a more 'normal' rainfall and summer temperatures means it might well have not been moist enough for it. They also prefer acidic or neutral soil, not alkaline, but were it that causing trouble, you'd have seen troubles earlier in the year.

Thanks for the comments, I did think it may be the tree. I have cut it back and will keep watering it, and maybe move it to another spot later. thanks again, it is much appreciated.