HELP...Drafty ceiling and wall vents-ANY SOLUTIONS??!!

Have only been in our house 5 weeks and it is cold!!! brrr brrr
It is open plan with lots of windows...we also have an upstairs with no door from the lower living to upper....

In the open plan family/kitchen there is a gas bayonet with a vent above it in the ceiling. Also 5 metres away there is a low wall vent in the cavity brickwork...(right at my ankles while sitting at the computer!)

There is an awful draft constantly through the wall vent and i can feel air coming through the one in the ceiling too! I have placed a plastic bag over the one in the wall with duct tape and you can see it blowing!!

What I want to know is..>WHAT CAN I DO TO STOP IT?

I know they are for ventilation so we dont gas ourselves, however as mentioned before the house is open plan with no door so the toxics dont stay in one spot...

How on earth this house reached its star rating god only knows...but im not happy having to keep the heater on and feeling constant chills!!

Hoping someone out there come across this before with an answer

What kind of window coverings do you have?

Do you have good insulation in walls and ceilings?

Any photos?

We have roller blinds downstairs and some upstairs with a few venetians...the walls are not insulated downstairs...upstairs is made of masterwall polystyrene stuff and insulated with batts too in the walls and ceilings....We have a drafty front door which i can do nothing about as it has to be replaced due to splitting...

Photos of what exactly?

I should add that i am in WA and the lower floor is double brick..

Hi! How big is the opening at your feet?

If it's tall enough have you considered putting in an operable louvre system like something from Klimat Louvres? You can use aluminium or glass blades and they seal up really well.

The smallest size is for an opening about 325mm high which is for two blades.

Thanks the opening is about 28cm wide and 20cm high