Just-ify

@Just-ify there are some inverters that has an AUX port / Gen port which you can use. 

The MPPT clips the Amps, no issue. Only the Voltage limits and max wattage are critical. 
 

I have previously used an external MPPT to charge the batteries using a busbar. The batteries, the MPPT, and the battery input of the inverter were all connected to it. Worked perfectly.
Biggest challenge is getting the charging settings right across all devices connected - e.g. synchronizing multiple MPPT or between MPPT and grid charging.
Other small downside is that the inverter obviously is always thinking that it was running on batteries while in reality the power feed comes from the MPPT. But that's only a 'display' problem and not a functional one.

Hey YellowTapemeasure, thanks for the feedback!

I'll obviously need a bucket full of advice, but from the bit of research I've done, I'd probably be in the market for a Sunsynk 5/8kw inverter with either a SolarMD 7.4kw LiFePO4 or a Freedom Won 5/4kw battery bank. I've heard good things of the SolarMD units and apparently, unlike  the Freedom Won units, they support adding additional units out of the box without limitations. Panels will be a second purchase most probably, after a professional roof inspection etc.

Hi, and welcome!
You must be referring to the PowerforumStore. They specified and supplied my kit, everything down to the last nut and bolt, and recommended a good installer for me, it was a great experience and the system still works great 15 months later, so I am sure that they can do the same for you. What kit are you eyeing?