Can't see a thread for this (may be I'm not looking hard enough!).
I realised the other day whilst out washing my car that the (front) near side wheel arch circular cover was missing, you know the bit that you remove to change the headlights (whoever thought of this ingenious idea needs shooting by the way!).
I contacted my local dealer and I've had to buy a "Flap Kit", Renault part number 77 01 474 633. You have to buy the pair, you cannot buy them individually. Only problem is, the flap for the offside wheel arch is like an elongated circle, so they are not interchangeable - another Renault masterstroke!!
For reference, the circular one just pushes in and turns approx. 1/4 of a turn, the elongated one snaps in to place.
The circular one's part number is: 77 01 055 351. The elongated cover's part number is: 77 01 055 352.
They are simple PP injection mouldings, all yours for just £15.66 (inc. VAT)!!!!

P.S. I did try about 4 local scrap yards, none of them had any MKII Megane's.