Find out model code for Samsun Galaxy 7 edge? Under "About device" I can see my model number is SM-G935F. However when I try and register my phone with Samsung it needs the "Model code/name" eg "SM-G935FZDABTU Galaxy S7 edge United Kingdom". 

How can I find this extra information?
see the long list of model codes for your device here.  (Since you didn't mention your country)
OEM says for S7, it is under the battery, so that's likely where you could find, but as mentioned by you , it's not removable

  Reboot the phone into the Download Mode (a.k.a Odin Mode) to see the Model.



( From the developer of Phone info Samsung mentioned in earlier question )