So the following expression is 100% polite and makes good impression?
Будьте добры (где стоит ударение?) скажите мне пожалуйста где находиться выход!
Yes. And actually no one should see any "rules" in strick black or white colours. I wrote above that "будьте любезны" sounds not well, but had a phone call today when some woman used that expression and it wasn`t sarcastic at all.