What the hell are they there for? A little grid, or lattice if you will, bored through the heavy plaster of my walls. One on either side of my bed.

They let in the cold and the noise of those angry buliders yelling obscenities next door - "I may be 40 mate, but i can still pull a 30 year old root!"..Urgggh, sure you can...

They feel so 1960s for some reason - my nan's house used to have them and they blended so well with the rest of her retro decor.

Perhaps that is where the nightmares get in...

I believe these are ventilation gratings or something similar. The one in my room vents to our attic, and there are a couple that vent straight to the outside through the walls.

Perhaps they're there to make sure that even with modern tight-fitting double-glazing, there's still plenty of oxygen getting into the room, and to provide an exit path for carbon dioxide and moist air.

Various types I've seen are floor vents (possibly combined with underfloor central heating), slim metal vents in the walls, larger metal-covered ones, small ones with closable flaps built into double glazing (if you have these, keep them open at night - they stop condensation building up, especially in bedrooms) and the ones fitted to our 1967 house, which are like painted perforated bricks.

CamTarn is entirely correct, they are for ventilation.

House building is a constant battle between the needs of the inhabitants (for warmth and comfort), and the needs of the building (ventilation etc).

If timbers are not ventilated, they will quickly rot. If rooms are not ventilated, the moisture you give off will not escape, and the walls will sweat, and the wallpaper will go mouldy and fall off the walls.

If you have a gas fire in your room, and it can't get enough oxygen, it will produce carbon monoxide as a by-product, which will prevent you from enjoying it's warmth for very long.

Overall, you need ventilation all over your house (grates between rooms), and airbricks to the outside world. However, they should be placed so that draughts do not cause a problem. If you're ventilating a fire, have the vent on the wall or in the floor near the fire, so that the draught has a minimum distance to travel.

Radiators are ideally placed in places where the vents are, since the cool air will be warmed immediately, rather than travelling across the room before heing heated.

The advantage of vents is that you can place them where it's convenient for the required ventilation, and you can then block up all unwanted draughts (for example, those from under doors and around windows).