There are several threads about fitting aftermarket seats, but the forum search function appears to be broken at the moment. When that starts working again, I'd have a look through and see if your particular seats are mentioned. The main considerations are whether the new seats fit on the same rail spacing (I believe the Up!s are narrower than many) and whether the electronic monitoring connector - for airbags and seatbelt alerts - will attach properly (most likely not, as the car's connector appears to be VAG-specific).
I've been following this great little forum since new year, and now I hope you can help me with info yet again.
I've got a Move up!, but I really miss having cruise control. And as I am under education, I'm hoping to be able to install it cheaper than the ~£500 it costs at Danish...