The importance or system design.
What you really need is an inverter that will be running at it's sweet spot for most of the time, and one that starts up with relatively low input from the panels therefore runs for longer every day, of course the weather each day is different in the UK so you can not get it perfect.
Now your panels are 3.5KWP per roof, the max they will produce under STD (standard test conditions) without any losses, but you do have losses, cables(correctly sized this are kept to a minimum), inverter, dirt on panels(I know you can clean them but not every day), orientation, degradation of panels over time, etc etc.
If your system was south facing your size of inverter would be about right, but yours is East/West, so the sun will be lower in the sky morning/afternoon whilst shinning on your panels.
Your system will most likely peak at around 2.5KW per array IE morning and afternoon on a perfect day, as your inverter is a 3.2KW it will take more power to start up than a smaller one per array and not be running at it's sweet spot, also when the sun goes around to the other side it is likely to shut down as there would not be enough power to keep it running.
If you were to choose something like an SMA TL5000 which has two inputs for different orientations, (or maybe a little smaller TL4000 maybe) then in the morning if the east is performing well then whatever the west is producing, no matter how small would be added to the easts figure, instead of having to wait for the sun to come around to generate enough power to fire up your 3.2 inverter.
You do also have to take into account panel voltage/ inverter voltage so that they are matched for output, this is a little more complex on a split system on different orientations and these parameters can be changed in some inverters by an expert, however they are factory set for a reason.
I personally like split systems like yours as it gives you a much more usable power curve for a longer period compared to a south facing which sees a very high peak midday, and overall, if designed well will produce almost as many KWH's per year.
If you are going to stick with your inverters then wire them close together leaving enough cable so you can change to one correctly calculated inverter in the future.
I believe I have stated before, this is an investment for 20 years, so if you can design a system that will produce a little more power every day compounded by 20 years, you will reap the rewards.
I have not mentioned your make of inverter, but I guess you know what my thoughts are.
