Well class C needs radar and if tower is seperating you there are different rules to when radar is seperating you even if you are IFR. If you say the wrong thing you can be completely on your tod.
For example if you request a visual approach IFR and you are given one. From then on they only have to pass traffic info and seperation is the pilots problem.
The are alot of folk out there who don't realise the rules that ATC actually run with. Personally I have never seen them written down in any pilot training, the only reason why I have a rough idea is multiple pints in the pub with ATCO's and 10 years experence and various bum clenchers.
Alot of pilots think they are seperated from other traffic when they actually arn't and its up to them to look out the window.