Speaking as someone who has had serious problems with a solar water heater installation, I think it is essential that there be a consent. And that the final job should be signed off by the certifying plumber
who is then responsible for its operation. Not a building inspector from the council who isn't a plumber and wouldn't recognise a problem if he fell over it. In our recent case, the local council was forced to recognise that they had been slack and they have had a major discussion about how to improve their "inspections". This is still on the table and there are ideas floating around. You might like to contribute. eg. There are certain dead give aways that should alert them to the fact that the installation is not as it should be. For example - a Caleffi air admittance valve installed at an angle without its isolating valve.
When our major overhaul was completed, Not only an inspector but also the man who manages the team of inspectors came out to discuss with a delighted young plumber exactly what he had discovered and what he had done to fix it all. They poked about and asked intelligent questions, revealing they were more clued up than they had been before. They have plans not yet finalised about how best to tighten up inspections, making the plumber the expert with the final say.
Our case exposed the fact that there are grey areas where responsibility for the installation is unclear. Our installer genuinely believed it was not his fault. He had carried out the work as he had been "trained" to do it. I don't know how he got his bit of paper - but it didn't do him any favours. It seems to me that this is a specialist plumbing job and it is crazy to allow someone who may an excellent salesman but with only a bit of on the job training from all accounts, to actually do some of the plumbing. Then the whole job gets signed off by the certifying plumber
who was employed by him to do the rest of it? This is not good, for obvious reasons.
If I were to be giving advice to anyone contemplating putting in such an installation, I'd be saying to go to a firm where you can be sure that the whole installation is done by a team of qualified plumbers, and to know where the responsibility lies if there are problems.
I'll update this when the council has finalised its discussions. At least there is some dialogue going now.