Steffan,
I did manage it once on the MZ. After buying it in London (Jack Nice RIP) I had to ride it back to Gwent at running in speeds down the M4. Managed something silly like 70 mpg plus by staying under 50 mph. They will do it, its the owners that are the problem.
Do the journey, getting any spares needed posted out.
The main advantage of the MZ over the Enfield is that it will run faster longer if required, and weighs less. That noise could get a bit trying though. 2T oil - I wonder what availability is like this days ?
Richard