Warranty Issue & Transmission Repair Advice (Toronto BMW)

Hi All,
I own a 2002 MINI Cooper that has a serious issue and I am not getting the appropriate response from my dealership service department.
The auto has 117,000 KM on it. I bought the vehicle after a 3 year lease and purchased it after at 74K with an extended warranty of an additional 40K.
At our service mark as recommended by the car, we brought the vehicle in for servicing (Oil Change, etc) approximately 2 weeks ago. My wife brought the vehicle in. When she brought the vehicle in she mentioned that she was hearing a pronounced grumbling sound below the vehicle, the same sound she had mentioned earlier. We have mentioned that the engine was making a sound during previous visits but this was not marked on our service record. Previous attempts to rectify a clamp sound were noted but ignored, instead being fixed the next time after we were adamant about it.
They replaced our brakes for $1400 (not needed according to successive visits to the dealer) and do not have a record of it.
What we found out was that they would like us to pay for the transmission, even though we were only 2K outside the warranty at the time. They continually delayed and did not respond to our requests.
They also mentioned that they found metal shavings near one of the plugs during their investigation and that the transmission might be loose.
In the process of this service, BMW damaged the rear bumper when washing the car. The dealership admitted then denied that they would repair the damage afterwards.
I have elevated this request to the service manager but he is not responding. He would not meet with me for even 15 minutes to discuss the problems and view the bumper. The last conversation was that BMW would pay for half of the cost of the transmission, only after we paid for the investigation to open the transmission up.
The service has been astoundingly bad. BMW Service for one year could not determine the source of the sound and did not note it on my file for my automobile. Hence, they feel that half of the cost of the part would be adequate as compensation since it cannot be under either warranty (BMW or extended) as there was no note of it on their files (which I have not seen). I believe that I got a bad transmission part and that I am not getting my due attention as a current and still potential BMW product owner.
I am wondering if anyone could give me any advice first on the transmission issue. I understand that the MINI manual transmission is sealed and once it is open it needs to be replaced anyways. The cost for the a whole new installed was told to be $5000 CDN. Since my vehicle is older, it is not worth my while almost to pay this price for something that should have been covered. Even with the half of the parts cost being offered by BMW, it will still be $3500.
Secondly, how can I get this resolved in order for it to be covered as it was covered but was not repaired during the warranty period due to dealership incompetence? Do I need to escalate this action higher to the manager above the service manager? I am willing to do this. I am also willing to contact BMW Canada to try and address this problem. I am surprised that there is no goodwill within this dealership considering the negative press they could receive from their actions (including this email thus far).
You advice would be appreciated.
Kind Regards,
Michael M. Stahl
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