Not sure why this is posted in the ideas section but ..

there are some inverters which are weatherproof to the extent you mention - you will need to research them. 
Batteries also but temperature will affect performance (temperature extremes).

Other options might be in the loft space ?

Thanks BPLightlog for your reply, is there a better section for my question. 

Had been informed it is no longer recommended for batteries and inverters to be installed in lofts which is why my only alternative was outside.

I will ask for this to be moved and tagged ‘smart home’ or similar - ideas are generally proposed improvements rather than questions. 
I know of several who have inverters and batteries in the loft and although you need to be careful of high temperatures, I would have thought that outdoors would not be much better. 
My system is in the garage and does not take up too much space as it fits to the wall and can be above a car position (assuming there’s headroom).

I do also know of some who have their system fitted under a canopy (or carport) but as you say, it will need an enclosure to maintain safety as well as security 

BPLightlog Thanks again for your help.

I don’t know these companies but there are a few sites who make suggestions

https://www.fitsolar.energy/keeping-solar-batteries-outside-the-dos-and-donts/ or

https://nxtgenenergy.co.uk/blog/solar-inverter-placement-in-your-home/