Just got this email from Apple:
Today Apple announced a new Mac Mini. Accordingly, we are pleased to revise your recent order by substituting the original product you ordered with the new Mac Mini at no extra cost to you. The new configuration either matches or exceeds that of the original product. In fact, depending on the configuration you ordered, you may be entitled to a partial refund. If you are paying by Credit Card, Loan, or Leasing, the price will be adjusted automatically.
The new Mac Mini is basically the same as the old one but includes 512MB of RAM as standard instead of 256MB, and the 1.42GHz model includes Aiport Extreme and Bluetooth as standard. I’d gone for all these options which means that Apple should hopefully be refunding me £46 very soon.