Dan,
I tried it on hot water only mode on the programmer this morning ( this being a cold start before any of the usual premature shut downs).
It ran, but only for 2 minutes, maybe less. Then shut down and showed a code "1" on display.
I then tried just central heating, with room stat still off, the boiler showed code "0" for thirty seconds, then went off and the display went blank, the code "1" from before didn't come back.
I turned on room stat and code "1" reappears, boiler then starts up and runs for 5 minutes, shuts down to a code "1" again.
JBPHS,
I changed the temperature to 70 degrees as you instructed which made no difference at all. The original temperature was 80.
I will try and get a pic of the PCB wiring.
Agile,
I checked the pipes. The one going into the right hand side hole gets warmer first and is always hotter. According to the manual, this hole is labelled "Flow" and the one on the left is "Return".