very much depends on if your conservatory is centrally heated/warm or a cold box.
Jade plants
You could try English Lavender.
I leave my potted lavender out all year round but it's probably my healthiest shrub in the garden.
Funny you mention that, I just ordered one of those after reading how hardy they can be.
That would be nice actually, they do look nice and smell good, natural air freshener
I assume you can just cut them back without issue? They tend to "grow out" dont they but with it being indoors, will need to keep it "in check" to a certain degree.