here are some photos that might make things clearer

pipework
http://i86.photobucket.com/albums/k8...pipelayout.jpg

one end of electrical bit
http://i86.photobucket.com/albums/k8...ann/oneend.jpg

other end of electrical bit
http://i86.photobucket.com/albums/k8...n/otherend.jpg

Having now had a closer look, its a Honeywell 9123. Info on the "other
end" gives a part number for head replacement - is that likely to mean
that the electrical bit is removable?

I have tried "rebooting" but nothing moved. On closer inspection, the
lever slot is marked Auto on the left and Manual On on the right.

I have now found one combination of lever position and on/off settings
where the lever does move under its own steam - If I push the lever to
the right, then put Water ON while heating is OFF, the lever moves back
to the centre position


Thanks for taking the time to help me to understand this

Steve