Thanks very much for your replies. I was told to contact the engineers directly not the letting agent. I think im being a wuss and not wanting to phone!
Hi all please be gentle with me, going to explain as best i can.
Had an alpha CD13R boiler installed. Worked fine until i put both the hot water and the heating on at the same time, then the bottom floor radiators all went cold while the top floor was tropical. So turned the heating off. But...