Update - I decided to take both bits of advice
I called BMW customer service and logged the issue. They claim not to be aware of rust issue and asked me to get my local dealer to take a look first. I agreed but got them to give me the Dealer principles details as this matter was so serious.
I have emailed the principle, telling him BMW have passed on his details and asked for his full support in sorting this out.
Lets see if that gets a good response.......I hope so!