Options for a Fabia vRS mk 1 upgrade

I've recently acquired a Mk1 Fabia vRS SE. Comes with the standard Symphony head unit and a CD changer. Which is nice. However, the radio isn't as good as the Sony I had in the older vRS, and I really need an auxiliary input, since I use a Garmin GPS as a music source and hands-free for the phone. While the Garmin has a built in FM transmitter, its a bit noisy and prone to interference, so I'd like to be able to use a direct input for the GPS.

I've got a pretty good Sony head unit, but so far as I can tell, that would lose me the ability to use the CD changer. I had thought that there was an adaptor for the Sony bus connection, but haven't managed to find one, so it may not be available any longer.

I know that there is an adaptor which would give me an auxiliary input for the Symphony, but so far as I can tell, it uses the same input line as the CD changer, so it would probably lose me the use of the changer as well.

As one further option, I've been offered the head unity from a 57 reg Octavia Scout. Its a double-DIN unit, so I'd need a an adaptor, but I'm not sure whether its compatible.

So, my questions....

Anyone know of a way of using the Skoda CD changer with an after-market head unit like the Sony range? Anyone know if the Octavia head unit can be used in a Mk1 Fabia? And if so, anyone know where I can get a suitable double DIN adaptor?

Just a few questions....