I finally , with the help of a fellow forumite , upgraded to a Lithium bank.
All is working well and I can now “pull the plug” on my grid feed and only use it as a alternative supply on bad weather days. (at R6.70 a unit it did not make sense to keep it on all the time) .
I have a Haggar 220v contactor that cuts the grid feed to the Multiplus and I am using a SonOff Switch to control the contactor. I would prefer to control it directly from the Venus as it would be a lot more reliable and should I loose connection to the server it will still be able to be controlled directly from the Venus.
From what I could see on the net the Venus’s relay is happy with 220v - 6A , so I should be ok to connect to the live feed from the inverter to the Venus’s relay that will control the contactor?
Right 
?
Seems you’ll need another in between relay according to the docs at Victron GX product range [Victron Energy]
This is a pretty normal practice, quite a few installers use this method together with the generator flag, to bring in the contactor.
You can use the Generator start function of the Gx, easy and self explanatory.
Cool , it just seems quite a lot more robust than relying on the server via mqtt…
Another way, which will free up that contactor too, is to configure the Multi to ignore its AC input.
This is completely untested, but I’ve used this in the past to do something similar. What you do is you set up the General flag assistant to ignore AC-in 1.
Then you set up TWO relay assistants. One of them will drive the relay on, the other will drive it off. If none of the assistants match the conditions you set, the relay stays in its current state. Set these up to read the auxiliary input on the Multi.
And then you set the other one up the other way round, so you have something more or less like this:
Now remember the sense is inverted. When the “relay” is on, that means it ignores AC-in-1, so the grid is actually off. Conversely, when the “relay” is off, it sees AC-in-1, so the grid is actually on. Swap your configuration such that your Aux input works correctly with the GX device (I think it is the wrong way round in this picture).
Then simply connect the relay in the GX device to the aux input in the Multi. Now the generator start/stop function can open and close the contactor in the Multi itself.
Edit: The extra advantage of this, is the relay in the GX device sees only 5V. All the wiring is now low voltage.