If it makes you feel any better (I think one specialist quotes close to £400+ for the belts and tensioners on here, whilst another quotes £250 although I struggle to see that when the parts alone are around £200...) my Clio 172 is far from a cheap belt change and makes a 944 look easy!
A local garage quoted me £460 + parts (around £170 from Renault, and oddly £220 from ECP!) with him not knowing what the dephaser pulley was :/.
A very local specialist quoted me £550 and possible £170 on top for a dephaser pulley (inlet variable valve timing pulley driven off the oil pressure)
The cheapest I found for the belts was a known specialist in Nottingham who charges £360 or £550 if the dephaser pulley is changed.
In the end I had mine done at a cost of £600

. The bloke was quite close and well known in the Clio Sport scene. Furthermore my dephaser was rattling a touch at idle with the belts being due on the years (5 years) but not on mileage where it was 30k under the schedule. I was tempted to risk it but the car would not even be worth scrap value with a snapped belt. They are a pain to change, none of the pulleys are on keyways and the tools to change them with are not cheap which is why I gave it to someone else (parts alone for the job were close to £300 with the oil and filter being part of that due to the dephaser pulley being changed). I remember a Porker specialist telling me that "they are not pleasant to change' and succeeded in sending me elsewhere as a result!
People have done them without loosening either the bottom crank pulley or not the cams with slight power loss issues or worse clipped valves. I actually saw the latter happen on a Kangoo 1.5DCi from a botched aux belt change; that was a lucky escape!