Wrote to amazon.co.uk about the delay. This is the response I got:

Dear Paul,

Thank you for writing to us at Amazon.co.uk regarding your order #xxx-xxxxxxx-xxxxxxx.

I am sorry for any misunderstanding this issue had caused.

Once you place an order on our website that particular item gets automatically assigned to your order from our inventory which are in stock at the time you placed the order .

Rest assured I have researched your order #xxx-xxxxxxx-xxxxxxx for the item "Nokia N900 Sim Free Mobile Computer with Maemo 5 Software" and I am pleased to confirm that it is on time.

We still expect to dispatch your order by October 26, 2009 deliver it by the date listed in Your Account: October 29, 2009.

Once your order is dispatched from our Fulfilment Centre you'll receive an e-mail confirming the date, contents and method of delivery.

[...]

Anyway, I'll probably get an email from them tomorrow apologizing for the new delay ¬¬