On Tuesday, December 20, 2011 at 11:10:40 AM UTC, Bob wrote:
The usual press time+ and select wasn't working, the battery inside would
prevent a full reset so this procedure does a total system reset.

Mains off
Unscrew with flat screwdriver the holding screw at the bottom of the unit
lift unit off backing plate pulling the bottom towards you
using a thin knife or a screwdriver lift off the back panel to expose the
circuit and the round backup battery
with a small bit of metal ie your screwdriver breifly touch the contact
below the battery to the outer case of the battery ( temporary short )
replace the cover, the unit is now reset to default ( you should be able to
see the display working again if you hold it at a angle )
place back on wall
tighten screw
turn on mains

There are two Select buttons. Which one to press with Time+?

Thanks
Mian