*Update* Just got back from the repair centre, spoke to a guy there who seemed like he was in charge.. Explained the situation and got him to come out and have a look, he did agree that there was a "slight" colour difference however he then proceeded to move round the rest of the plastics on the car saying he could see a slight difference in them too compared to the main bodywork.
That being said he was a really nice guy and said he could appreciate why it might could bother me, then said they do give a 5 year guarantee on all paintwork and seen as i'm not happy he has told me to bring it in during the week to see one of the "professionals" who does the spraying to have a look and see if they think they could improve the work.
He gave me two scenarios
1: The spray technician will agree that the work could be improved and do it again until i'm happy
2: The spray technician will say there could be no improvements and fully explain the reasons for the colour difference due to the plastics etc (Fob me off basically)
So i've come away not really knowing the outcome, one minute he seemed like he was just fobbing me off.. the next he seemed really understanding and seemed to be getting somewhere. The next step is going back through next week and seeing the technician, however I feel as if he might just fob me off and give me the whole "the plastics are always going to be different" speech.
Any help/tips going forward would be appreciated. Thanks Everyone!!