Salix of some kind, or Corylus, need to see the whole thing to even guess which one, and preferably with some leaves.

I will have to repost later, as there are no leaves currently. Thanks for the swift response.

Difficult from photo, but it looks like Hazel to me - they also have catkins on the trees at this time of year. A photo of the leaf in a month or so will tell the difference.

could also be birch.

Lots of possibilities, I will just have to repost when the leaves appear with a better view of the tree.

Hazel. Male catkins. If you look very closely at some of the unopened leaf buds, you should also see the tiny bright red female flowers (3mm). Worthy

Thanks Worthy.

Sorry Alex, perhaps I should have said Hazel instead of Corylus - they're the same, of course, but I tend to think in proper names rather than the common ones;-))

No worries Bamboo