Should I complete the gaps in the attic boards?

mark_cycling00

Dear all, I'm not too sure how my roof space is ventilated and whether I have a breathable or moisture barrier felt. But I do have large (30cm) gaps in the 21mm boards which I'd like to fill (allowing for expansion) because the "fibre wool" is a bit of a mess due to historic mice Activity.

So it's a 30yo roof with no visible grills in soffits or ridge. There is 50mm foam insulation pushed up inbetween the roof beams and under this is a later of material that feels like tough white paper and not that black felt stuff.

There's a walk-in bathroom inside this part of the attic and I can see that someone started to add foam panels to the back of the interior walls but gave up after adding only a couple in. 

Two photos show the gap and also what I found when I took one foam panel away from the beams.

I think this should be a fairly simple DIY job if it's ok and there's not a deliberate reason why there's such big gaps 

Many thanks