Does indeed sound very unlucky. Perhaps as a counter, the fact that there are now quite a few owners on this forum, and I believe apart from one other contributor that had a major failure, for which he explained MG straight away agreed to a replacement, should give some security that such total break downs are not the normal.
The Hybrid system is nothing particularly new, with all manufacturers offering some form of Hybrid across their ranges, so it's not a new untried technology.
If you liked the car, before cancelling I would certainly ask to test drive another, or even the same car if they claim to have fixed it.
Having had my car for a couple of months, the only major issue, which is something regrettably I think is common to all cars to some extent with ACC and LKA (semi autonomous driving), is 'phantom braking' where the car gets confused by a parked car and applies the brakes.
This I have found does occasionally happen.