It only seems to add water to bagged mix. If it could properly mix the dry ingredients (gravel, sand, cement, admix etc.) it would be worthwhile, so you could make concrete, screed, render, mortar etc.
Who has done your inspections to date? If you have a name it would help. Give him a call. Bear in mind it is the end of Easter hols today, so next week should be better. Unless they are no longer doing Building Control (which they are legally bound to carry out) you should be able to get someone out fairly soon. Be nice and don't lose your rag.
There will be loads of solar install firms who work near you. Get 3 quotes and pick one. It may be that they will not fit used kit or have wiring by others but you can ask.
I think similar or more expensive, depending on the range. Roseview are based on standard upvc profiles from Rehau and do lots of extra customisation and finishing. Their top range is almost indistinguishable from timber.
If you are not in an exposed location you could have got away without these as the render would stop water getting through. You probably have weep vents every 450mm but some have been covered by render.
You could have a dig about to find more or cover up any you don't like, but either way it is very difficult to make it match in with the render.