Hi Steve that price sounds pretty good to me if everything is straight, is it a UK car? I wouldn't be concerned with it being '04, pretty bullet proof motors.
I've never driven a Megane RS but i do know the Z is very different beasty to most 'hot hatch' type cars, the way it makes power, rear wheel drive, the lovely noises it makes. Id be very very very surprised if you were anything other than delighted with a Z...
For me, every drive is still an event, still makes me grin like a mad thing
I love my Z