Deezler's thread is
here and its a good source of info on TDIs - I'm looking to copy his Grill block when I have time...
Any of the models you choose will be good for FE, especially the Octavia and the Cordoba estates. The Passat is quite heavy but with an Octavia or Passat you may get a 6sp box - I don't think this was available on the Polo / Cordoba.
The 2nd gen Octavia is amazing for FE, my wife gets over 60 in hers and never ED's, and my dad has the 105 1.9 version and gets near 65 average.
If you can find one cheap enough also take a look at the Megane dCi estate (avoid the 1.9) or a Pug 206sw / 307sw HDi like PWs will give good mileage too. Astra estates are also cheap and there is a 1.3 CDTi option.