You're missing the point if you're worrying about 0-60 times.
It's about having fun. Get your Lupo set up right and it'll be flicky and drifty and huge fun.
Slower than an R32, but you'll be having masses of fun. You may find if you have a few track tuition sessions you can put a lot dearer and more powerful machinery to shame.
Without wanting to sound too much like a broken record, if you're doing it properly and actually safely you can't just a cage, or buckets, or harnesses, you have to do all three, or not at all.
If you are considering tracking the Lupo, have a look for the project details for an Arosa from a guy who posts as Drive Forward. He had a great little thing, full safety package, high quality coilovers, no engine work.
Barrel rolled it down Schwedenkreuz at about 110mph, pretty much walked away, although the whole car was scrap.
One of the nice things about the Golf2 as a track car is that it's lightish, with a longer wheelbase than a Lupo so it'll be more stable. It's also dead simple, so less likely to throw a fit and ruin your day.
As I think I posted in here already - any £6k car will probably need a significant amount of work done to even bring it to OEM quality - bushes etc will be shagged.
I really don't agree with the comment about the R32's parts being 'higher quality' than the Golf2. The Golf2 is one of the most extensively modified cars out there and there are a huge number run in race series and just as toys. This means there's a broad market of suppliers out there providing extremely high quality parts suitable for race and track day use. Probably far more than what's available for the R32. Because the Golf2 is so much lighter than the R32 it needs smaller, lighter parts, which all contribute to the overall lightweight and nimbleness of the car. All the heft in the R32 is the reason for the scary consumable costs - much weight = more material needed on bearing surfaces, bushes - just everything.
In addition to Nick's build thread, have a look at my Syncro chasing around some heavier-weight fire-power:
http://youtu.be/GUdKsoUn198?t=3m31sOh and this would be me making the case for a Golf Syncro as a track car:
http://youtu.be/h7slmZVSMzMIt's a lot harder to get it wrong, when it's moist.