In message 2020101823510528942-nospam@nospamcom, John Smith
writes

Be careful wiring in the new head as if the board is anything like ours
it's rather small and easy to forget what goes where and to
accidentally set another wire loose.

I have taken multiple photos and drawn a wiring diagram, just in case
:-)

What I'm not sure about is the two black wires which go into the valve,
from the cable to the boiler. One black wire is connected to an orange
wire, the other to a grey wire. Not sure whether it matters which black
wire is connected to orange and which to grey.

--
Graeme