can you resolve a problem with my double glazing?

we have 'breezes' of cold air from every new window and door we have had installed. They are upvc - company has gone under and we have no guarantee. You cannot actually feel specific draughts around the frames but the air 'blowing in' literally can be felt across the rooms. It seems to be coming from the whole window/door and there is a lot of cold air coming from them. It is far too much to be convection. Our house is really cold and we really are at the end of our tether with all this. Everything is really well sealed and we cannot work out how all this cold air is getting in. The frames, partcu;larly at the bottom are very cold but the glass (argon filled, black spacer bars and A rated) feels warm.