Its perfectly normal to get the 'jitters' when you are making a substantial purchase. I presume that you gave the car a good going over during the test drive?
From the pictures you posted - the car looks well cared for, but remember, no used car is exempt from wear & tear, however, all the problems you can read on this forum won't inevitably happen to you either. At least, you have the benefit from others' experiences, and will know what to look out for at the earliest (least costly) stages.
Many of the members have had more than one Renault - if the cars were so poor, that would not be the case. Also, if they were 'high-risk' cars, it would prove prohibitive to obtain aftermarket warranties - you know that this isn't the case either.
When I worked for Ford, all I ever heard was problem after problem - its very easy to adopt a negative mindset, but remember, there must be over a million Renaults on the UK roads, and a comparatively small number of these drivers have been motivated to join this forum for assistance with their issues - I'm no mathematician, but the odds are in your favour.
Try to relax and enjoy what should be a pleasant experience - you're not waiting on Death Row for the first problem to leave you high & dry!