anyone know how to get these off?

They can be a pain
They have a clip in them you need to flick out then you need to push back the o ring clip then just pull the pipe off

so is they must have pipe inserts then that can be removed?

so if i was to replace them with silicone hoses presumably they would have to go back without this fixture?

I don't think you can as half the fitting will still be attached at the car end

so ill have to make my own fittings up then.

pull the plastic ring back then pop off the pipe 🙂