In the new extension, the pipes hidden so cant see it, i know one thing, when i drained the kitchen rad from the drain point, the other 2 with the drain points still had water in them, how i know that is, when i filled the boiler with water via the loop, i went to bleed all the rads and the 2 rads with the drain points didn't need bleeding, soon as i opened the bleed screw, water came straight out, all other rads, had air.