From my personal experiences these guys have been excellent, as long as you can stomach a week's wait or so for delivery you can end up saving a considerable amount. They also stock like-for-like products like Army Painter and P3 Paints which can be harder to get a hold of in the UK Highstreet.
My recent purchase came to £130 for a whole lot of Paint Brushes, Dark Angels and a couple of the "5 Man" boxsets of Tyranids and "3 Man" Chaos Marine boxsets. Saved about £50 overall. £28 for the hard back rulebook was worth it over and over.