Apple Trees

Morning all!
I'd quite like to plant an apple tree in my garden (we already have a fruit bearing pear tree which is nice). I wonder if anyone could give advice? I only have room for one, so would one of the types which has several types grafted on be the right choice, as they would self-pollinate?
There is an orchard of sorts behind our garden with some apple trees in, but I don't know the types, so I don't know if a) they would pollinate a tree I planted and b) if they are too far away anyway. I'm living up to my name again
Also, are there certain types which are smaller in eventual height?
I've seen some dwarf varieties which are suitable for container growing, and you can then have a few together to pollinate, but I'd rather plant one out if possible, to look more natural.
Thanks!
Posts
Ah, thanks Logan! I was looking at the T&M ones so will consider myself warned
Jacksons have some multi grafted ones that look nice....
There are lots of good specialist suppliers out there and many offer great advice such as https://www.ashridgetrees.co.uk/gardening-advice/fruit-tree-growing-guides/buying-apple-trees - http://adamsappletrees.co.uk/default.asp - http://www.deaconsnurseryfruits.co.uk/product-category/general-family-trees/general-family-apples .
Personally I would avoid multi-grafted or family trees and just choose a single variety that you really like and would use.