I'm not familiar with this variety of Plectranthus, but after reading the attached link i think it will only be an annual and as a result will likely succumb to low temperatures.
Thanks for sending me these links @yorkshirerose and @madpenguin . Yes, the plant does look very tender, and I did wonder if I would be able to take some cuttings. Another plant/cuttings to put in a jar of water. The plant is just flowering now, which seems to me to be late for a tender plant. I will look for some nonflowering shoots and give it a try once the flowers have finished.
Posts
https://www.rhs.org.uk/Plants/201488/Plectranthus-Mona-Lavender-Plepalila-(PBR)/Details