I'm not sure that being Class A rather than D will make a difference in terms of airspace infringements (Heathrow still gets a few). Airspace class is to do with speed control, separation, minima, etc.
I've always found Stansted to be very helpful (returning to the original purpose of the question) if the second call includes the information "remaining outside or below controlled airspace". This normally elicits a thank you from Essex Radar. I guess if I was that busy and stressed at work, I'd be grateful too..
h-r