Hi Claire, my apple trees aren't producing much fruit this year either. I think a lot depends on the weather conditions at the time of pollination. This year we had some heavy rain which damaged a lot of the blossoms. Late frosts can also cause a problem. Also if your tree has two varieties grafted onto it that may mean that each variety polinates the other, if the one didn't flower then perhaps there was not an adequate polinator for the one that did flower, hence low production.
You need to keep your trees well fed thoughout the growing season otherwise they can become starved and not produce well the following season. I scatter a couple of handfuls of fish, blood and bone meal every few weeks around the base of my fruit trees throughout the growing season i.e. about March through to end of October.
One of my apple trees has the curling leaf thing that you talk about but only affecting a small percentage of the leaves. I have not been able to find out what causes it but that doesn't seem to affect the apples, last year I had a bumper crop. Provided it doesn't get worse and it doesn't affect the production of apples I am inclined to leave it, I prefer not to use "chemicals" if I can help it.
