It's incredibly naive to expect VOSA to do anything to the MOT station, how would they ever prove the car didn't have the bulbs in when it went there? They can't and won't even try.
I wouldn't waste too much time, energy or money trying to get mney back on this if it was a private sale
Depends on how many complaints they get about the station. They might not necessarily act on the word of one person but if they get several or even dozens of complaints?
Would they not act? It's not likely that they'll be handed concrete evidence by standard consumers.
I just had to report an automated phone call today on the ICO website today, individually it may not mean much but people are punished.