It looks like a type of linaria - there are many species and a few hybrids out there -

Thanks. i was hoping it was something benign like that!

Lilaria purpurea could fit, it is a short lived perennial and selfseeds, prefers well draining soils.

Thank you. i think you’re right.

Yes, Linaria purpurea. A common opportunist on my allotment. It should self sow if the seed head is left alone.

Thanks. i’ve left the flower head to form seeds and i’ve taken some cuttings too.

I’m not convinced cuttings will work with this species. Let us know how they turn out.