I have just managed to sort this problem for about 2hrs work and £5.
When it started leaking (soaking the headlining around the sunvisor) i did some research and learnt that renault have actually brought out a new seal for the sunroof to sort this known issue. It is £35!, for a piece of adhesive foam rubber about 1m long. Being a tight student type i decided that i could find the same for less. I managed to pick up a roll of draft excluder for £5 from homebase. This is adhesive on both sides, so i left the top layer on.
You fit it by:
Removing the seal around the interia of the sunroof, this releases the headlining. I also took off the grab handles and a few other bits like the light to help access. There is then about a dozen 10mm bolts. Using a ratchet ring spanner (saved me hours as there is very little room to work) i took att this off. With a little encouragement the top part of the sunroof will then lift off the car completely. Leaving the metal frame underneath the skin there. Take this out as well.
Once they are out, i removed all the tape/silicone that renault fitted.
You put the foam rubber onto the metal frame on the side that pushes against the inside part of the skin of the car. (as per renaults instructions for their own not so cheap fix).
Then on the top part of the sunroof i removed all the silicone that was on the underside of the plastic trim that comes into contact with the top of the roof (also cleaned up the roof). I added clear silicone sealant to the underside of this.
Then replacing all of the bits as they used to be, the sunroof pinches down and a load of excess sealant comes out which i wiped off.
Its been 3 days now and it seems to have done the trick. No more wet headlining or puddles on the seats. Just got to remove the water stains from the seat now. Any tips?
Hope this helps someone.