Is it easy to remove the plastic panel from the outside of a door?

Thanks Stuart, exactly what I need, I knew someone would have a photo.

Robin

Warmth, Warmth and Warmth. Heat it all up to make the plastic more pliable, this will stop it breaking the clips or the part of the plastic trim where the clips fit into,

Thanks Martin. Are we talking hairdryer or heat gun? I guess a blow lamp would be too fierce.

Start an argument with the wife and get her to breathe on it

I wasn't aware you had met my pet dragon?

If your wife and pet dragon are out on the day you do this, can I suggest the following (less green) option.
One of these:
 
These are great for working in front of this time of year, it also sorts out the panel warming you require.
Failing this a hair dryer or heat gun may help, but it's going to be lost on such a large area unless you can target a specific area. Both not as good as a just waiting for a warm day or the above heater.
You could just accept you will break a few clips and have replacements ready for the refit day.