you really need to go into writting on this one, a trail of signed letters is better than half remembered conversations , write a formal letter to the manager stating either
1. that you reject the vehicle as not fit and that they have had ample opportunity to resolve the issues and you expect a full refund to be paid within 48hrs of reciept of the letter, quote the documents above kindly posted by "eyesu0"
2. or set a date that you expect them to have fully resolved the issues and returned the vehicle, i would even push for that you expect to be compensated for the time you have been unable to drive the vehicle you paid for i.e next service free, (good will gesture)
in both cases set timescales for written responses and to be fair, do spell out what you intend to do next if timescales are not met or a satisfactory conclusion is not achieved i.e seek legal advice, go to trading standards, the media
the leverage you have will be your consumer rights and media related i.e watch dog and what car, local press etc, remember this is a premium car for peugeot
if you are a member of any of the breakdown organisations, certainly the AA used to offer legal advice
alternatively you could turn up at the garage at peak time naked and painted bright red demanding to see the manager - think they may take notice then
on the subjeect of them wantiing more money, what do they think this is a part exchange ???? get your money back and then if you want, order another one
Almost forgot - keep copies of everything youe send/give them
hope its all gets sorted for you - VERY SOON