We had ours ages ago, just turned up unexpected which is a tad inconvenient when you have to dedicate so much time to them .
If I remember correctly, he spent at least 2-3 hours with us going through everything, even how we dealt with customers and if we had a complaints procedure in place - what the hell that has to do with VOSA I don't know.
The bloke was very fair though (not our usual VOSA inspector)but you never know do you if they are leading you to the slaughter house or not !
Got "reported" for not pulling down "efficiency reports", nothing has come of it apart from a letter telling me what i needed to do in future.
I was led to believe that the function of the visit was to assess whether we were "good, fair or downright dodgy" garage's so that they knew how often to visit us.

Regards
Dave