I grow hundreds of fuchsias from cuttings.
I make a mixture of roughly 50/50 compost and vermiculite. I use Erin trays (roughly £2.99 for three trays) which are widely avalable in B&Q, Woolworths, etc. The trays hold 60 cuttings. Take the cuttings as small as possible. Two small leaves, with evidence of a growing tip, above the cut off leaves. At this time of year, it is important (obviously) to keep them out of direct sunlight. Growing them in trays, I do not use the polythene bag method. I have never done this and have always had very good success rate. Neither do I use hormone rooting powder.
I am a bit of a fuchsia addict.
Sunflower, at this time of year, you will not need the polythene bag method. As you say, your greenhouse is warm, and to be perfectly honest, with a polythene bag over your cuttings, they would be steamed!! Sorry Sanders!!
From personal experience, any cuttings you take now will need to be kept warm, but in permanent shade, and also well watered.
Good luck, I wish you every success, but be warned fuchsias can become an obsescion. I know, I've been there. But it is a wonderful harmless hobby. They are beautiful flowers.
valmarg