However the retailer is now saying it will be available both online and in-store from December 26.
The smartphone, which is the first handset to run the new Linux-based Maemo 5 software, features a 3.5in 800x480 display, along with a slide-out qwerty keyboard, 1GB of memory and the ARM Cortex-A8 processor.
Users will also benefit from a 5Mp camera with Carl Zeiss lens and dual-LED flash.
The Nokia N900 is available on a 24-month contract, priced at £35 per month and can be pre-ordered now from Vodafone, the Carphone Warehouse or Nokia directly.
See all mobile phone reviews