Sam mate, I've owned and run small and big business. From what I can see, rack it out, get a forklift. Get a manager in office. You need staff in the office, streamline your process, you need warehouse guy to do all the odd jobs. Your right about your installers, drop off and go back out. Your staff are the key to getting things right, just keep trying and never give up.
I also try to serve the high end of the market, its a tough gig, after all the money you make or save with solar is a pure mathematical sum based on the equipment you install. So we are competing with firms that put everything in the loft and never use scaffolding to install panels. My only advice to you would be to try to grow a maintenance division alongside your existing installation division. you can offer service level agreements to your existing installs and charge more to take on new clients that don't have the right paperwork or safety equipment.
I agree with @BillsCountrysideAdventures , racking would make really good use of the height you have in the store. You could then load the vans with the forklift too, let the stores person get stuff ready and the installers just come in, open the back doors and get loaded up.
I can help you with some of getting back office work like getting the vans organised and vehicle service organised so you can get more productive time for the technicians to work faster
Great insight on the progress your making. What type of solar panels does your company use at the present and is there any new technology coming down the pipeline. Thanks Alan