The Aliexpress link you posted in your previous post is the 6GB Note 5 (Chinese version) with the global ROM flashed onto the phone and it doesn't have band 20.So I may have been confusing myself above with the global rom Note 5 frequencies. It seems it does support B20:800 I just had to scroll down a bit rather than reading the product specs.
So based on that you don't need the official global version of the phone. The 4gb global rom Chinese version for around £160 should suffice.