I do also think there were several options.
I put a Blaupunkt Frankfurt to my S1 car!
It is the same building year and fits (to my mind) best of all possibilities!
The cool thing ont the Blaupunkt radios is !
They have a (I think it ist called Plug) DIN-Stecker, which bridges the Radio and the Amplifier.
You can buy a switch with two cable lines, and then you can play your mp3 Player , for example in your glovebox, throgh the old radio, and if you want listen to the radio,
you simply switch.
For me the best thing in any way, cool original looks and "modern" music.
The Radio fits if you cut a little of the plastic panel on the left and the right (abou 3mm all).