does it have blue and red stripes too? if not then it isn't Chrysolina cerealis

More likely to be the Rosemary beetle Chrysolina americanum

https://www.rhs.org.uk/biodiversity/rosemary-beetle

whether it will be nibbling the Phygelius I am not sure, but a good culprit for the lavender

I didn’t notice any blue stripes but it did have fine red ones, so possibly the Rosemary beetle as you suggest. I have put them in a clump of wild Evening Primrose as I didn’t want to kill them, I guess they won’t be too happy with their move! Ty for your reply.

that makes it most likely to be the rosemary beetle.
if hat unhappy they will fly to where they want to be haha