Here in the desert, they usually take 7-10 years from seed, so I suspect that you have some time, Bertie. It may take a little longer where you are, anyway, since you have a shorter growing season than I do.

Thanks for the answer; I guess we'll have to wait a bit longer. Some of my malus baccata started to flower and fruit this year, so I'd become a bit optimistic.
Growing trees from seed is a great idea but I think you need to be a bit younger than I am to be sure you will see all of them flower and fruit.