Hi Roxy, initially I could feel by hand that there was a difference in heating across the board, so I got out the IR thermometer and there was a gradual decrease in temperature from back to front. The centre of the board (where the thermistor is) is close to the set temperature, the back about 10 degrees higher and the front about 20 lower. The glass is in good contact with the bed, and the same problem occurs with just the board with no glass on it.

I had planned to do some measurements, as you suggested, prior to doing any soldering.