honeyman wrote:

Thanks Jim, I'd always wondered. So for max number of varieties in a
given space go for cordons and for maximum yield go for as big a tree
as possible ?

Or something grafted on a dwarfing rootstock. There are also some family
trees with two or more cultivars grafted onto a single rootstock.

They are expensive and a bit more trouble to maintain but you can get
heavy crops of two different apples out of the space occupied by a
single tree. I have one and it crops surprisingly well. Obviously not as
many as on a full sized tree but still more than we can sensibly eat in
a season.

Worth choosing the cultivars to suit your local growing conditions.

Regards,
Martin Brown