Renault seem to be a bit mean on the accessories/other equipment like parking sensors cc/sat nav n so on IF it wasnt fitted at the factory.
Maybe they allways were
On my mk 3 megane the sensors came fitted new (should be mandatory on the coupe cos of the limited rear vision) but thats another story.
Anyway they are integrated into the electrics/
and use the same beeper as the reverse engaged, lights left on , key card in ignition etc etc.
Aftermarket meg 3 parking sensor fitters, Ive seen on here buy the
Essentially its a control unit that beeps (from the sensors) and is powered from the reversing light circuit.
I think the units are around 20 quid?
You might be able to use the sensors you got with the bumper with one of these units.
If not at least the bumper is drilled already.
getting renault to upgrade the system probly be expensive!.. doesn hurt to enquire.