hi andy when the camshaft dephaser pulley wears due to a design fault which as now been moddified there becomes movement in the pulley this pulley alters the timing hence why it might sound a bit rough my advice if you get the genuine timing belt kit off ebay for £89.99 from a renault specialist ask for the dephaser pulley and water pump at the same time if you can afford it you might get discount pulley approx £120 ,water pump £45 and then 5 hours labour on top it worth changing these parts because if one fails you would have to start all over again as the timing belt operates these parts.
I've just had mine done on my car, payed for by the dealer who i got the car from 3 weeks ago.
The engine was quiet on cold start up but as it got warm it sounded like a quiet diesel engine, the noise disappeared around 2500rpm.
The performance was sluggish too and a little bit thirsty on the fuel.
The dephaser pulley was changed along with the cambelt and tensioners, now the engine is very quiet, performance is noticably better and fuel consumption looks good.
Cost = £508 inc parts, labour and VAT.