As you said, they fixed the headlights. In terms of the failure to do updates to fix radio and other entertainment reliability bugs, plus any recalls, it could be that the update servers in China were down so they couldn't do them on the day, hence the request to rebook. If this happened it was out of the dealer's control. A revisit should cure that. The blower temperature is a known issue.
Unfortunately, many EVs are like this at the moment with software bugs that require fixes. MG's system for updates is problematic but so are some others. VWs have had huge issues. MG do need to do better.
As you say MG is the cheapest, so you cannot expect premium service or quality. If you want a trouble free experience you'll need to either stick to tried and trusted tech, hope for better with a different make, spend a lot more, or buy a car that has been out for 2 years or more and thoroughly debugged. By buying an EV, you are effectively buying at the bleeding edge into an immature technology. There will be issues and "but I spent £25k-£30k!" doesn't change that.