If its Arbutus unedo, it could easily be after this last winter - they're not fully hardy. Make sure there's no new growth anywhere before deciding it's a goner though.

I am not sure if it is unedo or menziesii. Its 9 years old and in full tree mode about 12 feet tall and 10 feet wide from a very strong central trunk. The browning started gradually about a month ago and now covers 3/4 of the leaves. It has lived through frosts before here in Scotland but of course this last winter was tough. Is it better to wait and see if all growth stops or cut back some branches which have browned?

A. menziesii is also a little tender. I'd be inclined to remove any obviously dead wood, but it won't make much difference to whether or not the whole thing dies.

thanks - it will certainly be missed if it dies.