Been having problems with this pretty well since first fitted 3 years ago. Various parts silted up, despite power flushing. It now looks like the 3 way valve is on the blink - central heating coming on with DHW only programme. problem is, can't find a replacement. Saunier support seems to only want to talk to CORGI registered fitters, and it's difficult to identify the right part number on the site. Anyone who knows these, it's (I think) called the actuator - long black plastic part which attaches to the motorised head. Has a broken O ring at the very least, and looks pretty gummed up. Anyone help?