What would you do

Last year I used a large wood burner in the greenhouse but using it took a lot of wood and I felt that it was getting more difficult to provide wood for it, so I removed it, I had intended to use an electric heater, but with the temperatures we have been having over the past several weeks makes it too costly, but I also have a small pot bellied burner, which I could run to make the greenhouse a bit more comfortable to work in, but wondering what others would recommend doing

I used to have a woodburner in mine. It made it very comfortable to work in early spring when I was pottering about and outdoor temperatures were low. I only lit it when I was there and didn't try to heat the greenhouse for plants growing, or as you say it would have cost a fortune.
I must admit that once it was alight and greenhouse was 'toasty' sometimes very little got done as I sat around the stove.

That's a long sentence (doesn't have one full stop even). Until you mentioned work near the end, I was going to say just wait a few more weeks till it warms up, when judicious use of an electric heater over-night might be doable. Do you need to work in the greenhouse? I've been known to sow seeds on the kitchen table. If your greenhouse is large, you could put up a temporary (or permanent) partition so less to warm up and may be insulate?

If its to heat you, not your plants, either wear another jumper or stay in the house.
I don't see the point of suffering in the cold and the soil will be too cold for sowing seeds anyway.

I sow all my stuff in the house. Currently have a tray of 18 Lychnis just potted up and about 30 larkspur to go.....along with 4 mushroom trays of dahlias that I've started for cuttings. I may have a few other bits in here too

I have more seedlings in my bedroom than in the garden!!

That's a long sentence (doesn't have one full stop even). Until you mentioned work near the end, I was going to say just wait a few more weeks till it warms up, when judicious use of an electric heater over-night might be doable. Do you need to work in the greenhouse? I've been known to sow seeds on the kitchen table. If your greenhouse is large, you could put up a temporary (or permanent) partition so less to warm up and may be insulate?

But then I was asking about a gardening question not anything to do with whither my question was phrased in a proper gramatical sense:rolleyes :

I sow all my stuff in the house. Currently have a tray of 18 Lychnis just potted up and about 30 larkspur to go.....along with 4 mushroom trays of dahlias that I've started for cuttings. I may have a few other bits in here too

I have more seedlings in my bedroom than in the garden!!

I have been bannd from having seedlings in the house Scarlet, the last time I had them in the house, I finished up having to replace some flooring.
Sadly Veggie, my windows can't accommodate seed trays or pots.

Have you tried the tea light and terracotta pot trick...lots online about it.
No idea if it works as I don’t have a greenhouse...have I mentioned that before?

Have tried them in the past Jay, but not really suitable for what I need, I have a propagator with a cover and several nights it has dropped from 19c down to 11c overnight, once I have some plants on the bench I will be using a fan to keep the air moving, so might try them then, will let you know how well they work