There are plenty of garages that do cheaper MOT's, some also do free MOT's with a service.
Exactly! 
However be wary, as some certainly 'look' for extra work 
Yup, and official VW stealers are not exempt from that either. Just think of all the completely un-necessary 'air conditioning' services they offer!
If air con isn't broke, it don't need fixing - verging on scamming, is that!

Interesting you should say that. The one and only time i used a main dealer for an MOT(about 9 years ago), the car came back with a few faults that i don't remember seeing when i checked the car over.
The brake lights stop working, a tiny hole in one of the cv boots, and both front brake hoses 'bulging'.
Not suggesting that my car was 'tampered' with, but especially the cv boot was very 'iffy'.
The main dealers usually put the cars out to another MOT place anyway, so i went back to where they put it in, after doing the work myself.
Something definately didn't smell right, so i'd never use one again for a private MOT.