I have had my doubts about the dealer since, it was a few years back now. I now use information from local services in and around the area depending on area of concern. They are all time served with BMW main dealers.
I understand that all items have the exception to the rule, there will always be cases of malfunction. The M-power engine is near indestructable but I'm sure there are owners that have blown them.
The quote was making reference to the fact that the dealer had never had to replace a timing chain for the reason it's considered a lifetime item. Reading back though I can see how it confused. Sometimes I read and press post then go back after and realise it doesn't seem clear. My appologies.