That mpg figure is just about exactly what I get from my 2.0 T-FSI too. Around 270 miles around town, which equates to abt 26 mpg.
On a long run it is abt 32/34 depending on the speed I can keep up, but on slower country roads it can go up to 36/38.
Town is a killer though, esp if your runs are short then the engine never warms up sufficiently for the average to climb over 20!
Don't know abt the bike rack but if I were you I wouldn't have one custom-made; it can only be a matter of a (short) time before one comes out. Type 'VW Eos Accessories' into Google and see what you get; there are quite a few sites with plenty of bits and bobs and would be surprised if bike racks are not there.