Do I have to buy fruit trees in pairs?

Quite a few modern varieties are self fertile - it should say on the packets, or search the varieties online.

Most people use a different variety that flowers at the same time. There are lists of compatible pollination partners online

Also, what about your neighbours gardens?  When I bought my apple trees, I assumed there was a good selection for cross pollination and most were self fertile anyway, but then read up on Bramley apples and realised that it was not going to fruit without a partner.  However, there were no more trees for sale so I left it for the following year.  Amazingly the tree produced fruit that year and then I found out that 2 gardens away thery had Bramleys 

Crikey its starting to hurt my head lol

We live in an end of village location and I was going to put them at the end of a paddock which will be 200metres from anyone elses garden. We currently have 3 different apples trees and a cherry tree in the garden. My aim was to make this orchard which will be around 50 metres from our garden. I have also built a bee hive and would like to look into keeping bees which im hoping will help with the pollenation. The bees will be in the orchard.

Thanks for the link to the online calculator, im going to make a note of the types written on the tags and then see if they need any special treatment or a partner.