Just sharing some experience - this is probably obvious to anyone who has been doing this for a while...

On sunny days (we do a get a few in the UK) - post curing in direct sunlight or wrapped in black plastic can get parts up to 60 degC - if you are really lucky it starts off cooler and warms up as you get the full heat of the sun later in the day.

Then for the rest of the time or when leaving parts outside isn't so convenient I picked up a 2nd hand double electric blanket with 3 heat settings.  Arrange it as insulation, the mould & part, electric blanket, more insulation (I used old duvets covers/rugs).  With the blanket on max heat setting and doubled over I was getting the part to 65degC and of course temperature was even across the part, temp changes were gradual and its something like 50w so much cheaper to run than halogen lights.
I've post-cured a couple of small-ish parts this way and it seems to work well.
Next will be a bonnet so I'll see what temp we can achieve with the blanket in single layer (with plenty of insulation).


Stuart