Depending which part of the UK you're in, it might just be that the top part of the tree has not fully opened out into leaf yet because of the weather conditions this year, that is, the very warm February and the recent cold spell. Even here in the south of the UK, some Acers have been slow to leaf out, especially at the top, and in some cases, the new, upper leaves have been burned back by frost.
This is an Acer of some variety, but, in the images which show the top part of the tree, it's hard to be sure that some of the leaves don't have a white or cream variegation round the edges. This might be just an effect of the light, but it would help to make an ID of the variety of Acer if you could confirm or deny whether this is the case. There is certainly no evidence of variegation on the lower leaves visible in the penultimate photo. The other question I'd ask is whether the leaves on this tree turned red before falling or not last autumn.
On looking again at the images, the final picture shows some growth near the base on the left hand side that looks to be variegated, with white and maybe a touch of pink. Can you confirm that is the case? If you inspect the foliage, you may notice some all green branches as well as variegated ones, if what I'm seeing is variegated foliage in some parts at all.