It was a direct drop-in replacement for the original. Fitting it was pretty straight forward and the capillary pushed all the way in, unlike the original where whoever had installed it had folded about 3 or 4 inches of "spare" into the cable trunking, presumably because it had snagged before it was fully inserted (the capillary lengths are identical).

The old unit had required a setting of between 6 and 7 (almost certainly as a result of its improper installation), whilst the replacement needs only to be set around the 4 mark. I'm monitoring with a calibrated thermocouple to identify the optimum setting.

The relatively wide hysteresis demanded by this design of fridge makes this a protracted process but I think I've finally found where the optimum setting now lies with the replacement thermostat.