Sales of the Mii will start next spring, and while prices have yet to be revealed, sources have told us it will cost less than 8000.
As with the Skoda and Volkswagen, the Mii comes with a choice of two petrol engines 1.0-litre, three-cylinder units with either 59bhp or 74bhp. A five-speed automatic gearbox will be an option.
There will be an Ecomotive version that's capable of 63.7mpg and emit 97g/km of carbon dioxide, meaning buyers won't pay any road tax or London's Congestion Charge.
At launch, just a three-door version will be available, but a five-door will appear later in the year.
As the cars are mechanically identical and there's not much difference in price between the entry-level versions of the Citigo, Mii and Up, buyers will be likely be swayed either by the cars' looks or by the level of equipment offered.
Seat says the Mii can be specced with City Safety Assist, where a laser recognises other vehicles in front and whether they are driving or are stationary. If an accident is imminent at speeds of less than 18mph, a warning is sounded and if the driver doesn't take action, the brakes are automatically applied.
Seat will also offer the Mii with the Seat Portable System. This uses a five-inch portable screen that combines sat-nav and a hands-free phone system. It also has what Seat calls an 'Eco-trainer' function that helps owners learn to drive more economically.
Seat says this can be kept up-to-date with internet downloads and tailor-made apps will offer additional functions in the future.
Equipment levels have yet to be revealed, but Seat says there will be plenty of personalisation opportunities for the Mii.