Difficult at this stage. Could be a lime (Tilia species, not Citrus), but it seems over-twiggy.
If you could show a close-up photo of one of the most-open leaves, that would help a lot.
Also, if there are any remnants of fruit/seeds from last season (perhaps at the base if the tree), they could also help.
Thanks; useful, though now I'm thinking elm (Ulmus).
We may have to wait a tad longer.
Was it bought as an ornamental tree or fruit tree?
Any luck with seed/fruit remnanats in the little at its base?
Beneath any tree, remnants from leaves and fruit will tend to occur. Yes, those things may also blow-in from nearby trees/shrubs, but most such material will come from the branches immediately above. The fruit can be very useful in diagnosis: beech nuts or their husks, chestnuts or their husks, maple keys (samara), hawthorn berries, etc. In spring, many such pieces will tend to be obscured as grasses and herbs start to grow up. They will still be there; they will just need a bit of probing-for.
Yes Jez it certainly could - good call - it looks good for Betula pubescens, downy birch. But we'd need to see if the new shoots are downy - a bit later in the season.