Hi
Off top of head I paid about £26 for the top mount, its not a dealer only part ebay or motor factors stock them, mine came from a motor factor, the top mount usually causes the spring to break, you usually get a strange sound from the front end when on full lock mine showed up mainly pulling out of Aldi as it was an uphill junction and hard over left, can't discrbe the noise really it is really quite odd, not a grind nor a bang more of a odd sounding rub, some time got it revesing onto my drive as well seems to make it when the spring was not under that much stress, as with Aldi left hand down but pulling out so weight on righ hand side, reverse onto drive (on hill) right hand down but backing down hill and turning right so with the hill most weight again on right hand side left side makes a groan, thats it! A GROAN, did this for a few weeks but not always, so you wonder and think Ooo must look at that, then BANG! as I went over a speed hump, boy was it a bang, then poor old Meg leaned and limped home wimpering "I've hurt myself" bits of spring feel off as we trundled home at 10mph it broke at the bottom of the 1st coil at the top, it was luck really it was that high as it enabled me to drive home, carefully but got her home.
Strange we have had a Suzuki in for MOT and failed it on a broken rear spring and lady said "oh, I did hear a bang about two months ago, and thought it handled differantly" she had been driving for two months on a broken spring. Again it had broken right at the top.
Just A thought though, on your old spring are colour codes, I bought my spring from the same motor factor as the top mount, car sits fine no leans handles ok apart from when it is windy it then feels slightly "out of balance" now I don't know if this is due to the spring or at 89k I am having shocker issues. budget wise the spring and mount where a LOT cheaper from the factor than from Renault and you are also told as with shocks always replace both on an axel, so I do wonder even if I had bought the over priced Renault one would I still have this issue as I didn't change both springs to match, may be I should have bought both springs from the factor but then you start thinking where will this end, means a strip down of the driver side a swell so car off road for even longer plus when you come to change the spring will the top mount fall apart due to age so that is another £26 to spend, just thought I would let you know changing one side may give you an issue, I don't find it dangerious just a bit anoying sometimes, I think it is worth passing both plus and minus on, you could put yours on and not have a problem, so just thought I would let you know this is what you may get.
The main problem is that the springs are tapered top and bottom, which means that it is difficult to compress it far enough. I ended up using 2 compressors to squeeze to middle 3 coils, then 2 more to compress the top and bottom tapered sections. As Chris says, there is a lot of preload in these springs - to fit the spring you need to compress it to approx half the length it's length compared to it's full (off the car) length.