Ian Cundell muttered:

Well, I asked at Ayletts (big, v highly regarded garden centre round my
way) and the nice young lady said that her hazel was also pushing out
catkins already. She though it was probably the slightly anomolous
weather - the wind has been constant - and suggested putting some fish,
blood and bone down (as a more balanced feed than the bonemeal it got at
the start of spring), but otherwise leave it in peace unless it gets
really dry.

Ours did the same thing approx a month after planting but now it seems ok
again - so fingers X'd