Good result in the end.

Morgan are different to mainstream car makers. There is a feeling of closer contact with the Company themselves. I suspect this can encourage people to go direct.
As with any purchase the first port of call and responsibility is with the dealer the car was bought from (Sale of Goods Act etc).
The dealer has responsibility for putting faults right where they are appropriate.
Failure to do this means there is a well defined process with legal responsibilities.
I had similar when buying a second hand car for sospan jnr. Repeated failure to resolve issues and poor customer service meant rejecting the car. That proved sufficient to resolve without going to the next step of the legal route. The advice is to be firm and clear with the dealer, set timescales for resolution. Keep a log of contact/comments. Tell the dealer that a final chance to resolve is being made, after which escalation will occur. This can be in two ways.
1. Contact the manufacturer with details of the fault and the dealer's failure to rectify.
2. Legal action re recovery of money+costs. This is against the dealer.
Points to note based on advice from experts like Which etc.......
Keep communications concise, clear and non abusive.
Keep records.
Ask pertinent questions re what dealer has done/contacted re solving the problems. Ask for details of any contact with Manufacturer.
This tends to get the message across that things must be dealt with properly.
Avoid rants on social media. Maybe ok for venting frustration but rarely productive.
Even here on TM.......there have been a few but thankfully less so now.