You're missing out all the fun part Alistair.
I'm DIY king.
One of the electric blanket controllers is still working and it's basically a PWM unit with timer. (Just pulled the dud one apart to check the circuit ) so a change of plug will give me an infinitely variable heater controller from about 1 watt to 6 watts. Well within the controllers capability of 250 watts.
I've never had dew problems before but the weird wet warm weather and a refractor rather than a reflector has precipitated the urgent need. The controller is just a small plastic pendant which can hang down beside the pier no problem with timer and temp indicator glowing dull orangey red. Power cord will easily reach the dist panel just behind. Actually quite a convenient setup.
Total cost $0
Fun Priceless
