Have you checked to make sure that no fuses have been blown by water shorting something out?
May have popped an essential fuse. (ie; fuel pump etc)
Another problem could be a
sensor, don't know what kind of DIY job that is (never had to do it), I can only give general advice on this problem unfortunately.
One more thing that has happened to me that fits the bill is a short to earth in the engine bay, if a melted or broken wire touches to the engine block or bodywork it can cause this exact problem, so worth checking any visible wiring in the engine bay for chafing, poor routing and loose connections.
Come on Clio owners!!!, anyone got ideas or first hand experience?
Another possibility is a dodgy key - it should be kept away from speakers or other strong magnetic fields as most car keys can be affected by this.
If this has happened it may be that the immobiliser is struggling to "see" the key or something.
If the car has a spare key, try it before you do anything else.
Process of elimination....
I hope I'm not patronising you with all this stuff but nobody else barr SeanTDI has come up with anything (I agree to check the starter cables also) and from your thread I figure you may not be used to having to do all this stuff, if you do have experience with stuff like this then please excuse the no-brainer suggestions.
Other no-brainer suggestions would be:
fuel line leak/breakage (usually visible if you get under the car and trace it's route, also check the fuel filter isn't corroded and/or leaking)
Check the fuel tank for holes on the bottom (I once witnessed someone put a screwdriver through the bottom of a tank to get free fuel....GRRR
make sure all the spark plug leads are secure and clean.
check that the pipes that go to the air filter aren't blocked/clogged with debris.
I could go on and on as there's so many possibilities that can stop an engine firing....
If you haven't sorted it yet and can't afford a garage it may be worth spending a day checking this stuff, I'm quite sure you could find specific info on fuel filter,
sensor location etc on here if you use the search and "tag" features.