My tree is 2 years old - it flowered fine the first year, but the 2nd year didn't flower so well and only produced 5 apples. I think apple trees should begin fruiting in their 2nd year, so upon closer inspection I discovered I had a serious Aphid problem (which were easy to miss as they are very small, green, and live on the under-side of leaves).

If I were you, I'd have a close inspection of my tree checking for garden pests, as it should definitely have flowered prettily by now, at the very least.

also have you got another tree in the same pollination group

I actually only have the 1 apple tree, but I was considering getting apple bushes. Would this help?

Thanks everyone - I have a feeling I'll need to plant a pollinator. So many of my neighbours have other apples I didn't think it would be a problem. Can't see aphids, although it had them the first year and they were dealt with fast!