I want to grow some fruit trees, but where do I start? I don't understand pollination groups or rootstocks, or the difference between a stepover and a cordon and a maiden and a bush. Help!

It's a familiar cry. Folk quickly get bogged down when they're shopping for fruit trees, as there are so many varieties and options open to them if they want to do things properly, rather than nip down to the nearest B&Q and end up with the wrong plant. I'm faced…