Mad Jock: as far as I know, everything
except wind is mandatory - at least I can't seem to recall anything which ATC might tell you which is non mandatory????
For example:
"D-KC, Runway 24, cleared to Land, wind 240 20knots, caution wake turbulence."
I would read back as
"D-KC, Runway 24, cleared to land, caution wake turbulence."
I chose that particular example because some would say wake turbulence is an advisory and doesn't need to be repeated, that only instructions need to be confirmed yet whenever I land in Germany at larger airfields, if I don't read back "caution wake turbulence", you can guarantee that tower will then say "D-KC, confirm caution wake turbulence".
This could also be "caution, gilders / parachuters / radio controlled models in the vicinity" at smaller airfields.
Having said that, I did my PPL in Germany and have a BZF, not the UK FRTOL so maybe there are variations? It could also be that my memory is failing me in my old age
