I can recommend the Becker Cascade 7944. Single slot unit with GPS Sat Nav (all EU covered), Bluetooth phone integration, iPod integration + CD player. Had one fitted in my A2 yesterday by The Sound Gallery in High Wycombe and it works very well and looks stealth too. Sound via the iPod and iPhone is very good.
I understand that they are made specially for A4 or A3 but maybe take contact with them and see if they have one for A2, that would be great, and it looks OEM.