To be honest with you Penny I would not buy a tree from that source. It is advertised as bare root and it is long past the time for planting bare root apples. They are best planted from Autumn to early Spring ie not when they are in leaf. They are also offering two varieties which are not compatible. Bramley will not pollinate Braeburn and it cannot pollinate itself. Bramley pollination

I suggest you buy from a reputable nursery which gives you full information about the trees you are getting.

Most all apples need cross pollination. Buy two separate apple trees in varieties that you enjoy and make sure they will bloom and pollinate each other. The orange pippin site lists the best pollinators for each apple type. If you are lacking room you can stick two trees in a single hole and prune or train them as a multigraft.