If you mean the extractor fan, that's not what I mean, there is a potential for damp to build up behind the insulation, an extractor fan is not going to do anything about that.
No, I meant the wall and roof vents, but I've just noticed that they actually go all the way through... not sure if they still provide any ventilation to the "cavity".
I would have put a membrane (plastic or Tyvek) between the shed and the T&G and there should ideally be an air gap between the outer wall and the insulation.
It is a nice looking shed and I wish I had a shed like that. Just make sure you keep an eye on the walls to make sure the insulation is not soaked and you don't have mould etc growing in them.