Motor garages are either independent retailers, part of a group of garages like Arnold Clark, Evans Halshaw, Vardy, etc, or a very few are owned directly my a motor manufacturer.

Each and every one is free to set their own payscales so there is no point finding out the going rate in London if your brother is in Aberdeen.

He needs to get into the garages and find out what is available locally on both the training and the pay because everything else is just academic.