Welcome back.
Robin’s system and software is still available to constructors - all the (modern) details are on his website https://mk2pvrouter.co.uk/
There’s no reason why the two or more systems won’t work together - but each must not try to steal from the other. There’s a thread running at the moment about this, and I solved a similar problem with another user some while ago.
You’ll need to make sure that all systems can accept a control hierarchy. The system with highest priority needs to be seen by the one with the lower priority as part of it’s normal domestic load, and the higher priority system must not see the dump load(s) of the lower priority system(s).
The user whom I helped had just two systems - I think battery and water heating, and his problem was the two systems oscillated, stealing power from each other alternately. I suggested that he ran the wire feeding his immersion heater backwards through the grid c.t. of the other system, so its current in the main cable was cancelled out. So it knew nothing about the immersion heater, while the immersion PV system saw the battery charger as part of the normal house load, which automatically had priority. That solved the problem.
With the overall control strategy hopefully explained:
That depends entirely how the two systems want to interact, according to the type of installation the designer of the battery system envisaged or assumed.
Unless you do something like I’ve outlined, there’s every possibility of that.
If you decide that will be so, yes (given what I’ve written above).
[Edit]
Here’s the previous thread about a battery charger:
And the conclusion: