Two things I've learnt about MoTs...
Firstly, not all MoT testers are the same. Our P38 came with a fresh MoT with an advisory. Can't remember what it was, but it was mechanical and it's never been fixed. Since then it's been through 3 MoTs at different stations without a single advisory. So, either the P38 fixed itself, or 3 different MoT testers have missed something, or the original tester was wrong.
Secondly, you can get a fail for some really stupid things. Our VW Transporter was once failed for a leaf stuck under the driver's windscreen wiper.
The tester (Kwik Fit) didn't notice the leaf - just noticed that the wiper didn't clear the screen properly in the correct areas. When I told him I'd changed the wipers the week previously, he found and removed the leaf, and then passed it - and for the rest of time I was there got the p!ss taken out of him by all the other members of staff...

Serves him right.