In message , Liam38
writes

Help,
I suspect this is a weed. Can anone tell me whether it's a plant or a
weed.
Thanks
Liam

Weeds are plants. (One definition of a weed is a plant growing where it
isn't wanted.)

Anyway, what you have is red valerian (Centranthus ruber) in both the
white and red forms (there's also a pink form) which is a garden plant
which often escapes into dry habitats (e.g. walls, pavement edges)
--
Stewart Robert Hinsley