Susy, I wouldn't touch a patio heater with a barge pole. Too many -ve's and not enough +ve's (maybe none).
Deal with 'cold' with adequate clothes. Either layers and layers or visit the owl. (Brisbane cold???
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I've seriously considered heater strips but so far have avoided the need, even on the refractor. Don't underestimate the usefulness of passive devices. I have a pair of 15x80 binos which I used to use a lot mounted on an observing chair. They would dew up as soon as you looked sideways at them. I covered them in heavy Al foil (silver emits less radiation than black and hence cools slower) and made dew caps about 15cm long out of heavy foil and bits of tin can, painted black on the inside. Unless l leave them parked near the zenith I never have any dew.
Most of my scopes are gotos so the finders don't worry me. Eyepieces and the small binos are the main problem. I find that so long as every item that is not in use is under cover or in my dust and lint-free pockets I have no problems. On the 40cm dobs I sometimes have to cup my hands on the secondary holder for a couple of minutes but that's it.