Appreciate some help. The clock in this central heating timer stopped
going round and having spent hours trying to find a way to get into
the timer I broke the plastic lugs off. I'm not too bothered as I
wanted to replace it with a modern one anyway. It one with the old two
on and two off pegs around a circular clock.

Having got inside, it hasn't helped and now I'm stuck. The metal piece
at the back won't come away from the wall and it needs to to get to
the wiring which I need to do to fit a replacement. I still haven't
worked out how it was meant to come to bits but it looks like screws
from the rear and if so these are completely inaccessible. The people
who did this have cut a hole in a wall tile and so you cant get to the
very back of it. Anyone know how it is mounted?

When I do get to the back, what model can I replace it with? Are these
things fairly standard?

Some clues would be appreciated. I have replaced a timer in a previous
house but that was dead easy - nothing like this!

TIA

G.