Donwil

Just an update on my Tomzn change over contactors. They switch on and off every day controlled by a timer sonoff switch.
Its been about two months now since I installed it and am happy with it. These units are quite decent and the terminal screws looks quite solid. On the weekend I used a welding machine and there were a bit of heat on the 63A contractor but it looks like it will survive. I will definitely suggest these as a cheaper option.

What is the distance from this Combiner to the Inverter?
 
EDIT: You are aware that your lightning arrestors is not connected and offers no protection currently?
Its a pity that the installer plans to run all positive wires through one isolator/breaker and all the negative wires through the other. Effectively you will never be able to isolate one string at a time. Once you switch off either of the 2 breakers/isolators, all the strings are isolated. 
The fuses in this setup will not have any effect even after adding 6 strings as 3 strings will be combined on each of the 4 incoming connections of the 2 PV breakers. 
This Combiner  is designed for 6 strings in and 3 strings out. I would wire this completely different. 
Remove the bride pieces above the Fuse holders,  Take each string to its own + and - fuse holder. Combine the fuses at the bottom then take the combined feed through on 63 A Breaker/isolator to your inverter.  Use one surge arrestor for the + wires after combining them and the other surge arrestor for the - wire after combining them .  That way , you can isolate each string individually, your have fuse protection in a multi string setup, Something you dont have now as the combining will happen before the fuses, and currently the current of the string is divided over 3 fuses. And lastly, you will have one Isolation point to isolate all the strings at once when you need to work  on the inverter 

Hi @Donwil
There is a lot of info on this forum and on the blogs. But I can send some basic info your way here:
A PWM charge controller is designed for basic use and will not optimise your 400W of Panels, so only use this if you intend on drawing much smaller amounts from the batteries (eg: I use a PWM controller for my Camper Van, where the only draw is usually a fridge and a few LED lights). Secondly, most chinese controllers are very poor at converting your available 400W to something decent and many cant cope at the rated capacity. Rough calc 400W/12V = 33.33A so nearly already bigger than a standard off the shelf 30A controller can handle. As chinese controllers go, look at the ECCO brand with a LCD interface, but still only expect to get about 60-70 percent of your PV back in real terms. In full sunlight my 300W of PV through a PWM controller is closer to about 12A of charging current for your batteries. FORGET about chinese invertors! They Lie, Lie, Lie about the ratings, and they can get away with it for the most part. Just think about the price and it should give you a hint. Many of the chinese invertors out there that are rated even at 1500W can barely push out 500W before letting the smoke out. Just try find a decent invertor, possibly on this forum or web store, that at least has been proven (the small axperts, although chinese, are at least proven as basically capable by a few members here) Next is your load - You haven't specified what you are thinking of running off this small power plant? Is it your whole house, a few PC's? 2 x 12V 100Ah batteries will give you a maximum (if you don't plan on keeping the batteries too long and working at 50% which is reasonable assumption for Gel batteries) of 100Ah usable power (extremely rough calculations - I don't want to be shot down by the experts with the mathematical calculations and discussions about specific batteries). If you drain them at a decent rate then roughly 4 hours at 25A (300W - 3 incandessant light bulb or 1 or 2 basic Desktop PCs). Drain them slower at 10A, then about 10 hours (1 incandessant globe) I have a blog on this forum called "KLEVA's Lessons Learned", and my lessons have been expensive for someone with limited funds.
How to start? Well you already have some panels... For a 12V setup you will need to connect these in parallel to a decent PWM (or better if you can) Controller. This will be able to charge a decent 2 battery setup (also in parallel for 12V) to start with. But you are definately overestimating the amount of Load power you can feasibly get out of that arrangement, if you try draw 3kW (or kVA) out of 100Ah of available batteries you will only get about 20 minutes of power (and you are going to horribly stress your batteries)
Now that I have scared you, I apologise. You have some decent starting ideas, but you need to think a bit more carefully about your load and batteries to store the power. Your 4 solar panels have the ability to generate roughly 3kWh on a perfect day (your batteries will only keep roughly 1,2kWh and a decent PWM controllermight only just be able to supply that), so you need a better way of trying to collect that energy, store it somewhere, and to use it carefully.