Another 72 hours on and the level is holding. There is a tiny damp patch on the newspaper underneath but no discernable drop in the level. The temperature in the garage tonight was -1.9degC. After an hour with the fan heater on full, the best I could get was 2.0degC, although the pit is a balmy 5.0degC.
It doesn't look like I'll be doing much in there this weekend...........
