At Heathrow all of the terminals are separated by distance. This looks like a single building even though it is not so looks a little odd. Once inside they will no doubt be connected so passengers and visitors will feel as though they are in one building. At Bournemouth I had to step outside to cross the gap which felt very strange.
Stansted has the luxury of plenty of land for expansion. That very fact means it will have a great future and should rival Gatwick in terms of capacity for its single runway.