I am quite familiar with Europcar Stansted airport.
I have spoken with the SM on many occasions so if you need to speak to him let me know direct, I have his mobile..He's a nice guy and may sort things out!
Clearly europcar suffers from many one off tourist clients at Stansted so loyalty clients have an issue since there are no dedicated desk, even though the banner upon arrival is still there.
It is shocking that you had to wait 45mins. I would have gone mad too. And customer service have standard email answers these days. I have issues with them on a regular basis..it is not acceptable, but alas there is little you can do.
I feel for you as a long suffering elite member of their program myself, but I've learned that europcar is clearly about rates (with or without easyjet tariffs) and that's what you get, take it or leave it as it is often the case their CS tend to respond without offering any comfort.
I believe that there are a lot of complains there from regular clients and the more we complain to the SM or CS, the more they will realise that service is poor...