In your own words you stated that the PC was "editor's choice in the October 03 edition of personal computer world" therefore i guess lots of people might want this PC too. They might be having problems getting the parts due to demand or getting them built quick enough.
I would either wait until demand has gone down or get a written (e-mailed) delivery date or cancel the order.
You said yourself that you "have placed several orders with simply over last 3 years for various components etc without any problem" so maybe they are having problems this time. It happens from time to time.