well the 70mm ones are too small, I need some much, much bigger so off shopping.
The squirrels that were trapped seem to have figured out how to push the vents out. Quite frankly they frighten me, so have stuck up a light, flung some bleach soaked rags and am looking for new vents.
Its a bit of a lost cause as I need the drains to be redone, they show leaks at all the joins so will have to pay for a builder then and they can do the vents then, but I simply cannot leave it that long.