You dont need a master tech for servicing , any apprentice can change the oils on a zed , they are basic cars . You need a skilled fitter with experience of the marque when its in depth problem solving, certain upgrades , using diagnostic equipment etc for this experience is key
Anyone who can service a micra can service a 350/370 every other service is an oil change and inspection, takes 1 hour to do it thoroughly, hardly rocket science.
The reason I use an independent specialist rather than a main dealer is that they have a passion that main dealer lack