Hieracium maculatum ... spotted Hawkweed :o)
It's quite hardy in my garden here in Wales, but don't know if it would be with you.

We had it once and it took us years to get rid of it. Never ever let it seed.

It behaves quite well here - not invasive at all. It does seed around, but not a problem. Maybe the weather agrees with it :o)

Even came up in the lawn for us. Almost as bad as Hieracium aurantiacum, Grim the Collier.

Thank you both for your help. It was one of the more interesting looking plants that came into the swap, and I vaguely recall seeing it at a garden centre last year, but I didn’t have a chance to take a close look at it.
There seems to be a difference of opinion among sources as to whether it’s invasive (here), or how invasive it can be. I’ll try it for a year or two, but will make sure not to let it go to seed.
Thanks again for your help. Much appreciated!