[Centaur one]

I am speaking from personal experience as I had similar issues. My car is fitted with the media XL option, my iPhone 5s has the Mini connected options with web radio. The Mini directory has a Mini connected option when your phone connects to the car it is supposed to go on the internet and enable web search, web radio tune in etc. in my case it did not. There was a problem that required a software upgrade from Mini and they also had to replace my media centre. The long and the short of it is my Mini connected app now works and allows me to use web radio tune in etc. I also have the e call and car data transfer options these also work now and I am very pleased with it.

You need the options fitted in the car otherwise you are reliant on your handset as the receiver and this relays to the car which if course is dependant on signal strength and type. Do not assume you are using the car aerial etc for signal. From what you have said it appears your system is behaving like my last statement.