2008 Peugeot 207 steering out of line

Ive just bought a 207 xs 150 thp, when you hold the steering wheel straight it goes to the left. Ive taken it to arnold clark they said they put it on the computer and the wheels are in line.I took the machanic for a test drive and he said it didnt look right but some roads appear to be straight when there not, he is going to phone peugeot and get back to me. He also told me that they had alot of problems with the 308 last year and peugeot told him thats how the steering wheel sits and theres nothing which can be done about this and this could be the same problem wit mine. If you are on the outside lane of the motorway and keep the wheel straight the car will make its way into the inside line thats how bad it is. Shoyuld this be?