I can't say that Solartherm UK are the cheapest. We did get other quotes but they are the most qualified looking into them and have been in existence the longest so that was the decider. Job scaffolded correctly, paperwork arrived promptly. Warranty forwarded has come from the manufacturer and not some template with the installers name on it. 10yr HIES policy covering Solartherm. So I'd say we have played it safe and you pay for what you get.