I would do it a little at a time, using as little water as possible.
Spray a small amont of Autogylm degreaser on a chosen area, agiate with a soft brush for a few seconds to start it working, rinse of with a small amount of water or even better just a damp cloth, dry as best you can with a towel, move onto the next area. Doing a small area at a time saves getting the whole engine and parts you dont want to get wet.
Cover anything you dont fancy getting wet with plastic bags or cling film if your really worried, there is not anything I would worry about to much under the Clio bay, apart from avoiding the plug holes as long as you are careful with the water.
After dress plastics and hoses with something like Autoglym Vinyl and Rubber, polish the paintwork with Autoglym Super Resin and any shiny metalwork such some metal polish.