I was thinking more in terms of perceived loyalty and continuity? Or record keeping?
Again, I can only speak from what I have experienced.
I bought my pre-registered S5 from Stoneacre in Derby, knowing full well and telling them that I would not be using them for servicing etc, since the return journey home to garage was over 100 miles.
In the meantime my wife had had her older MG3 (petrol so not hybrid) serviced at a local MG dealership and was very pleased with the standard of work and the cost.
So, it was really a no-brainer that I would have any servicing etc carried out at the same dealer. I actually also took out an MG Service Plan with them.
In the event, following the disasters of the 12v battery going completely flat, 3 times, this same dealer has been exemplary, having the car in twice for extended diagnostic testing, once for three days and later for over a week, both without any hassle and the Master Technician who carried out the diagnostics was very helpful and explained fully what he had found. In the event there were "no faults" but MG UK have agreed with him that a new T-Box will be fitted (when MG dispatch it! But that's a different issue.)
Ironically, and perhaps inevitably, since the last diagnostic check the 12v battery has been faultless!