Blocking up 1930s Air Vents

Hello

Was just looking for a bit of advice i currently have these big metal air vents in a couple of the bedrooms and would like to fill them in.
They all have open shut windows and pretty good ventilation but they are basically big holes straight to the outside and really cold.

I have removed one and covered with a cheap plastic adjustable vent which to be honest looks horrid so would like the hole blocked now.
So whats the easiest way to go about this!!

Many thanks

Wayne

Remove the vent cover internally, remove the air-brick externally and any sleeving.

External - tooth out the half bricks and/or closures and brick up and point to match existing.

Internal - mortar in bricks to suit.

In both instances brush out all dust, damp down, allow to dry a little then apply mortar.

Lovely thanks for the reply noseall I will tackle this at the weekend or at least prepare it as its quite a big hole.

Regards

Wayne