I had a 307 too. 1.6 Rapier, and it was genuinely the worst car I've ever owned, and I've owned a few bad cars! I had it at 5 years old, and the heater stopped working, then randomly just came on a month later, alternator failed, had to replace the lambda, and had another random electrical fault that would make it go into limp mode for about a minute, then clear itself. It wouldn't save DTCs either so despite 3 trips to the dealership, no faults were logged. Considering I had enough and chopped it in after 6 months, I think it tells you something that I had so many problems! Car only had 46k on the clock too and bodywork was in good condition, so I don't think it had a hard life previously. Incidentally, it was my mk5 Golf GT TDI I chopped it in for!