I have a Micro Genius HE 24 boiler fitted with a Danfoss wall thermostat. The mechanical boiler clock no longer works so I plan to replace the stat with a new prog digital stat such as the Honeywell CM901. The problem is I cant get the old Danfoss stat off the wall. The dial can be easily prised off but I cant see any screws or clips either on the unit or on the other side of the wall.