Just to be safe, I would make clear plastic tents to put over them, large enough to give 15 cm of clearance between the plastic and the foliage. Without the tents, a lot depends on the variety of chili: some, like Jalapeno or Serrano peppers will have few problems, while Habaneros or "Ghost Peppers" may have problems with the chill alone, without freezing.

Thank you Tug. I hadn't thought of tents. I'll get S to come round and make them herself! I have no idea of the varieties of chillis but they are named so we could look them up.

I agree, my chillis are the first to bite the dust when temps dip below 50 Fahrenheit.

Oh dear, that bodes ill I fear, Bathgate!

Yes, chillis are tender and very sensitive to temperature -

'Plants will tolerate a minimum night temperature of 12ºC (54ºF), but better results are achieved above 15ºC (59ºF), and avoid temperatures above 30ºC (86ºF) as this can reduce yields'

https://www.rhs.org.uk/advice/profile?PID=664