Thanks for your answer, it's not the answer I was hoping for but it is what it is. Plumbing and heating is what I do for a living and I'm really good at it. You say they had two expert opinions but with plumbing and heating the bible is dictated by the manufacturer and what they say goes. The landlord wrote to the letting agent to forward onto me. The Landlord was wrongly advised about the installation and was proven so when I spoke to the manufacturer.