These threads are REALLY putting me of another BMW.
OP: my first port O call would be to write to BMW and ask them
"What is the anticipated lifespan in excess of for the timing chain and acilliary parts"
You know the reply will be useful in court.
Then small claims it.
With luck the 'reputational damage limitation division' of BMW will kick in and maybe gets settled before judgement.
Easily worth a punt - but SCC fees are more than stated and based on a sliding scale.
More likely a court fee will be in excess of £400.