The whole mileage thing seems crazy to me to own a TDI for a 9 mile commute. 20+ then yes. The whole actual mileage thing has loads of threads in this mk5 section anyway,including the old unleaded or super debate. In terms of the cry at the pumps when doing a 400+ round trip, my old GTI used to get anywhere between 280-320 miles to a tank with most of that being town driving...stick it on a motorway and cruise just under 60mph and 40mpg is possible, and therefore able to return 400 miles to the tank. That was a standard GTI with no mods at all.
Concerns for the old mileage cars goes with the territory, and do your research before you buy. DSG box cluncking or slow to change, whistles from turbo's, air-con compressors failing, along with both the small and main fans, and then you have misting from wet pollen filters, high oil useage, water coolant sensor problems etc. Rusty front wings from the inner arches rubbing is also common on earlier models like that ED30 rep. Just a point as well, the seats were ED30 and BBS CH (likely reps) along with rear bumper but the skirts and lower front valance were all just GTI spec 
Yeah i agree with my shortened commute its definitely more of an option to go with petrol. Before my golf i had a crappy 106 diesel (was all i could afford when my motorbike was stolen), and that returned 64mpg average. To get used to a car with 30mpg, its just a big hit to get used to. end of my moaning on that subject now.
Im probably giong to avoid the DSG box, purely because i enjoy manual, and after reading up on them, although they have raving reviews, im just wanting the simplicity of a manual.
dTEA, props on spotting the GTI spec'd bumpers, i hadn't clocked that

As it happens the garage this car is at has got some dodgy feedback when you google them, so i wont be looking into that car any longer.