...I now have the same problem: I've just been told that the wiring and logic rail have been incorrectly wired. Issues arising from this are:
1. No frost protection
2. No anti-cycling protection (which boiler uses to promote longevity/efficiency)
3. Over time, when the boiler cuts out, with water at max temp, because you're cutting the (only) live feed, the pumps won't 'run-on', and the pressure in the system local to the heat exchanger, may prompt it to leak/fail, prematurely.
No, I'm not fuggin' impressed with my 'SEI Approved' installer either !!