Help! white fly all over cauliflowers

You can spray with chemicals if you're into that, or just cover with fleece or Enviromesh to make sure they can't get at your caulis
You could try washing them off if there's not too many caulis involved. 

I just noticed I have them on my cucs in the greenhouse but getting rid of them without recourse to chemicals is not easy.  I'm still gettings cucs so not unduly bothered 

If you can use a hose on a fine spray that might be easier. We can't use hoses on our plots though so we have to use trigger sprays