Before doing anything check the contract you signed. The dealer’s T&Cs are probably on the back of the sales notice or some other documentation they provided to you when you paid your deposit. My VW dealer had 60 days post estimated delivery date to supply the car. After that I had 14 days to give notice in writing that I wished to cancel with no penalty.
Thankfully, my VW Up! turned up only a week late and I was only quoted 8 weeks in the first place, but I ordered back in March, by the time I collected mine, the dealer said there was now a 6 month waiting list.
If it is a standard spec and sought after then the dealer may not be too bothered and allow you to break your contract without penalty, but my main dealer’s T&Cs seemed very onerous, almost read like they didn’t even need to supply me with the car I ordered.
It is a fantastic car BTW well worth the wait