Willows like lots of water, they hate to dry out, which is why they do very well in waterlogged ground. I could say a lot of things about the ground in the south at the moment, but waterlogged wouldn't be one of them - it's possible that drought is affecting your tree, so give it a good soaking overnight by leaving the hose running at the base of it.
I'd add, though, that at 9 years old, that might not be the problem, so also suggest you inspect the trunk, branches and leaves for signs of infestation or disease - willows have several diseases which attack them.

thank you bamboo

do you think the cuttings and debris at the base of it could have a detrimental affect?

No.

thanks again bamboo

can't see any obvious signs of disease or infestation. had the hose on for @ 5 hours last night so fingers crossed that it will come back to life. the ground here is very dry. we do hose it each evening but not for prolonged periods which we will start to do now unless we have a hose pipe ban!

really appreciate you advice with this - this is the only significant tree we've got.

Hose it each evening, oh dear - please, please, read my blog on watering - click on my avatar and then select blogs on my home page - not too many there so you should find it easily.

good stuff, thank you.