Thanks to Steve for recommending that I should have a look at Soil Hill, otherwise I wouldn’t have found the Bristly Ox-tongue.
Bristly Ox-tongue (Picris echioides).
All parts of the plant are covered in stiff bristles.
It is not listed in the Flora of Halifax and according to The West Yorks Plant Atlas it is rare in West Yorkshire, only recorded three or four times. I’m not sure if this is the first record for Calderdale or not?

Narrow-leaved Ragwort (Senecio inaequidens) above and two below.

They were dotted all around the site.

 Hoary Mustard (Hirschfeldia incana).

The key character of identifying this species the presence of a seed in the beak of the fruit.

There were masses of Greater Bird’s-foot Trefoil.

Great Willowherb (Epilobium hirsutum).

Creeping Cinquefoil (Potentilla reptans).

Scented Mayweed (Matricaria recutita). Crushed flower heads are very aromatic.