Firstly I won't be touching or going anything... I only want advice if this is right.. my partners dad has a aga that is solid fuel unregulated heat source and a oil boiler. The problem the hit water cylinder doesn't have a stat thus why the hot water is roasting hot but there is a pipe stat on the flow of the coil to cylinder. There is a heat leak radiator in the bathroom.. is this system done correctly? When the oil boiler runs solo the hot water becomes really hot because there is no cylinder stat is it possible to have a cylinder stat fitted to the cylinder or even change the pipe stat location onto the cylinder it's self? What setting should the pipe stat be set at? I know these type of systems and dangerous if not done correctly but it's a system that was done 20 years ago.