Whats wrong with my apple tree?

Woolly aphid aka American blight seems the most likely. These are sap sucking insects which cover themselves with a waxy covering. Use a brush dipped in methylated spirits and remove them. You may well need to do this a few times to get rid of them all. Then spray the trees i December with a Winter Wash (Organic soft soap).
You also appear to have some leaf miner as well. Remove the affected leaves and bin them.

From looking at your picture, I think you are referring to the white fuzz around the buds - I do believe this is quite normal and I expect it's to help protect the buds in cold weather. If Owdboggy is right and it's woolly aphid, if you squash the woolly stuff between your fingers you will find the insects inside. But I don't think that's the case here.

With regard the leaf miner, if they are young trees and all the leaves are effected, then I wouldn't pull all the leaves off....they'll drop off soon anyway coz it's autumn.

then agine it could be powdery mildew, if so spray withsulphur carbendazim.three times at forteen day intervuls, as regards the leaf miner and the winter wash Oowdboggy has filled you in on that, you are on the job so you will to make the desions good luck.

I agree with Sid, re buds. With the leaf miner you can kill each one with your thumb nail, as they are small trees it shouldn't take long.

Yes, that "fuzz" around the buds is particularly noticeable on some varieties more than others. Bramley in particular though Blenheim Orange is another that comes to mind.