If your unsure use Masking Tape as I did but only use a screwdriver if needed very carefully on the housing at the rear once the unit starts to ease its way out don't use it as a prying tool as it will cause scratches as Neil's post pointed outThanks a lot guys.. I will try to find some plastic tools and give it another try, otherwise I must go to a professional.
Thanks for the swearing tip
Just push a plastic trim removal tool underneath and directly central to the light and pop out as previously stated they can be stubborn to pop out and it may be prudent to protect the paintwork.I have just ordered some, which are due to be delivered tomorrow. As a retired electrician, I have loads of tools available to me but knowledge is king. Any advice on how to extract the old units without causing any damage would be greatly appreciated. I don't want to use a sledge hammer to crack a nut.