🤣🤣 Oh bloomin heck - Something else to chalk up to experience, didnt cross my mind at the time, only later when thinking about the floor buildup. 

 

I was left with these two vents right under the front door.  Is there anything I can do?  Plastic isnt going to withstand years of trampling through the doorway, and wont support the finished floor covering very well.  I've got a good number of vents on that side of the build so I could chop em out fill and insert a brick.  Or...  Any other solutions?  

 

That's the inside. I'm puzzled by the height they reach up to. It looks like the top of the telescopic vent tube would be virtually the same as your floor finish. If they're all like that then there's a whole lot of cold bridging going on!

I've just pinched this picture so the wording on it is  not mine.  However the schematic is similar in that the telescopic bit is in the cavity enclosed in insulation everywhere else.  Except in this case this door the builder left as a single skin hence the vents being  visible and yes they are to the FFL which is the problem I want to resolve, and am looking for a bit of guidance.

 

I can't see the original photo. Might you be able to repost please?

 

Can you just omit the vents at the doorway? Are there enough elsewhere to suffice?

Ok, so the door is flanked by two fixed glazing units and everywhere else the vents are in the cavity. Building Regs (Approved Document C) requires block and beam floors to have ventilation on two opposing external walls of no less than 1500mm² per metre run of external wall or 500mm² per metre² of floor area, whichever is the greater. If your other vents combined provide this then yes simply omit the awkward ones. The mm² ratings of each vent should be stamped on the plastic grilles. Typically you get around 7500mm² per single brick sized grille.