Dwarf Apple Tree

YOu would be better growing a dwarf or patio fruit tree. Garden centres sell them. You need to look for M27 rootstock, they grow to around 6-7ft and are happy in a decent sized pot.
M9 root stocks are slightly bigger, and would need a larger pots.
Just remember to keep them fed and watered.

http://www.rhs.org.uk/growyourown/fruitadvice_rootstocks.asp

- gives you an idea of the types of rootstock and sizes they grow too and types of rootstock depending on fruit you wnat to grow.

http://www.rhs.org.uk/advicesearch/Profile.aspx?pid=359
Is a bit more helpful

Any garden should be able to help but make sure they know and cancan reassure you it is M27/M9! It shoule be on plant label

They also need to be in the same pollination group or self fertile. The GC should also be able to help

If you go to W***vale they sell apple trees specifically for patios and they even give you a choice of several to polinate each other or like I've got two apples on one rootstock which works out about 10-15 normal sized apples (so dont expect huge amounts! - just enough to be something special when you eat them!!) Just remember you are responsible for all the food and water and they do take lots of water and each spring I give them a top dressing of fresh compost just so there is extra food extra when they are bloosomming and tom food during the summer.