my first thought is a sawfly larva but as to which one I don't know.

Thanks Sbg I'll google it , the leaves are matted together with what looks like strands of cotton I should have put another photo on showing that ..the whole tree is suffering ..

I don't think its sawfly Sbg I have had that before and would recognize the little caterpillars ,Thats odd my previous photos have disappeared ...

Those little specs look like aphids - the katydid eats them. The big green thing is a katydid, they are related to crickets. They like aphids.

This is the bug Paul ,I don't know what happening every time I put a new photo on the previous one disappears .. I might have to delete the whole lot and start again ...

LOL I thought I was going batty! I keep seeing different bugs, lol .I don't know what those little wormy things are.

Thanks for looking Paul I hope someone comes up with an ID I don't want to lose the tree but then I suppose the leaves will fall off soon anyway with it being autumn .. Don't worry you're not going batty I guess it's the silly computer system ..

do they have proper legs at the front /head end and stumpy type legs at the back? or are they totally legless. if legless then they will be a proper fly larva ie maggot.

is this the first year there has been a problem? these are the only photos I have seen so missed the others!

It looks like a beetle larva, to me. I'll be looking for it, too.

No Legs Sbg it looks almost like a maggot , the other photos disappeared when I tried to add them on , this is a brand new tree I've only had it about 3 months it was expensive to ...
I hope you don't find anything like this on yours Tugbrethil ...

Hee, hee! Well, I'll be checking at work, but I don't own one myself. What I meant is that I would be checking the internet for leaf munchers that matched diet and appearance to your problem children. I haven't had much luck yet, though. A database of pest insects with pictures of their various life stages, diet, range, etc. would sure be useful, but I have yet to find such an animal.

Tug there are rarely books on the whole critters and life cycle. I know to our cost that there is a book on caterpillars then one for moths, butterflies etc. Dragonflies and damsels have a separate book just on the cast skins for heavens sake. Our youngest is gaining an excellent library of such books. having said that I have one on just the 150 species of isopods that include the woodlice! the internet just isn't really specific enough.

These larval forms are tricky to ID. They go through 4 or 5 molts before they pupate and could look completely different at each stage. I thought it might be a red admiral, but Forest Pansy isn't one of their host plants so scratch that idea.

it doesnt have any legs apparently so it cant be a butterfly/moth. Red admiral caterpillars are blackish and 'hairy'.

Thank you all for your kindness in looking for me ,I've gone through pages of bugs, insects ,leaf eating critters without much luck ,I don't like spraying but I think to save the tree I might have to ...

I'm thinking that the bug & the damage aren't related. It looks like a blowfly maggot to me, maybe there's a dead mouse or something nearby?
Could the leaf damage be scale insects?

Before spraying, I would grab the hosepipe, and give the tree a good wash with a strong spray of plain water, then wait a few days to see if it helps. You probably won't wash very many larvae off, but the ensuing cool, clean conditions will greatly encourage predatory insects and mites.

Darren I haven't seen any dead creatures around the garden we have a lot of gravel in this part of the back garden and theres more than one of these things wrapped in leaves , Looking through my books the one thing it does look like is Capsid bug I did knock a big green bug off the tree this week , a lot of the leaves are curled up with what looks like cotton threads ,not woolly ...
Tugbrethil thats a good idea I'll give that a go first of all ..

Mysterious... I know there are some sawfly larvae that make webbed nests

My guess too would be some sort of sawfly.
Just as an example of sawfly variation - it slightly resembles a very young version of Blackheaded Ash Sawfly - which it probably isn't (as wrong plant and wrong country).
See webpage:

http://www.donsgarden.co.uk/pests/496

However, things sometimes arrive from abroad and might adapt to new plants if their usual food source is not around?

you could of course send it to the Natural History museum for identification or to the RHS labs.
both take specimens for id and will let you know.

Thank you for your interest Longleaf I'll look at your link , I'm hoping it disappears when the leaves fall naturally Sbg if it should happen again next year that is what I shall do ..

That certainly does look like the larvae of the Black headed Sawfly in the picture Longleaf ,I'd better do as it suggested and dig up all the soil surrounding the tree to uncover any eggs , fingers crossed it does the trick ,I'll be keeping a close eye on it next year before it becomes a problem ..