So it seems the 360 is overtracked by about 130K for the UK by VGChartz. So far the website doesn't seem to have been very accurate with regard to the UK. Some major corrections with regard to PS3 sales in the past and 360 vs PS3 sales recently.
http://www.gamesindustry.biz/articles/xbox-360-to-hit-2m-in-uk--next-week-