never seen this before - do you know which Acer it is? Full Latin name? Only explanation I can think of currently is fasciation, but that usually affects stems and sometimes flowers, never seen a leaf do it. Otherwise a virus, if this cultivar isn't meant to look like this. Is it growing perfectly well anyway?

I have never seen that before, either. Is this the first year that you have had the acer or has it been there for several years - if so, did it look like that in the past?
The leaf looks very healthy so I have the feeling that it might be a cultivar and is meant to look like this, but I don't really know.

My goodness this looks unusual to say the least and puzzling, as I have never seen an Acer like this. How long have you had it, how tall is the bush, does it look like this every year. Are you certain it is an Acer? Any chance of taking a picture of the whole bush? I am really intrigued.

Thanks for the replies - its been in for three years and seems to grow ok. I get the feeling its supposed to look like that but the over all effect is really messy
I'll put a pic of the whole thing in my photos

Seen the pic in your Photos Howee, but can you take another one a bit closer as well - hard to see any detail in that photograph. I don't mean a close up of a couple of leaves, but closer to the tree so a lot of the leaves are clearly visible. Thanks.

I'm adding a couple more

Had a look at them - weird. I take it you don't have a proper name for this particular tree then, Howee, no label or anything? It looks as if some of the leaves are "normal" Acer leaves, and some are doing this funny curly thing, is that right? If the curly leaves are present on individual branches, so you've got, say, 3 branches with nothing but those leaves on, I'd be inclined to cut them out at the base where they spring from the trunk. If they're randomly spread in a mixed fashion, with both normal and these leaves on the same branches, there's not much you can do about it - doesn't look like a disease, though may be some kind of virus, about which you can do nothing anyway. So in the end, it's down to whether you find it attractive or not - if not, then your only choice is to get rid of it.

There isnt a branch that hasnt got them on, i will have the label somewhere, will have a root around. Going to leave it in, maybe when its a bit bigger it;ll come in to its own, its just always puzzled me

MIght be a new, fancy variety, who knows - that's why I'm asking about the label!

Think ive solved the mystery - saw some the same in a garden centre at the weekend Acer Palmatum something beginning with L, one of these daye i'll remember to take a notebook!