you are gonna have to dive through the back seat and get a small flat edged screwdriver in to a small slot in the boot latch, this will open the boot.
or does the glass hatch open ?
most likely is that you have had water get in the glass drain hole and leak from the drain hole (clear rubber hose or elbow has come off)
water usually gets into the electrical switches and messes the locks up.
WD40 the latch mech to clear it out. unclip the boot liner and take out both rear switches and check the number plate lights, they tend to fill up with water as well.
the elbow can be glued back on, its located behind the rear wiper motor mech'.
don't forget to drain the wheel well of the new lake in there (try knocking the plug in the bottom up to release the water)
you shouldnt need to replace the switches, just remove them and drain them and WD40 them, should work ok, mind the rubber if its perrished or feels like its slimy or melted then u need a new one (they are £25/35 from renault)
oh and those little plastic clips holding the boot liner that you probably broke are about a quid each
best of luck