I found a cure but don't know from where?... It turnes out the Graphics card timeout in regedit needed changing
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers
Check you have the following REG_DWORD
TdrDdiDelay
TdrDelay
If they are not present, create them and set the Decimal to 60
This worked for me and although there is a second of delay here and there, there are no CTD