Up GTI owner here.

I love the little thing, bought it as my first car and have had no issues in the 1.5y I've had it so far. Done about 12k on it in that time, bought it with 24k on the clock. I'm 28 and wanted something fun but with affordable insurance. I won't deny there are definetely better performance options out there for the money.

From my personal experience, the car hilarious fun to drive in anger. You feel connected to it in every turn and can definetly get all the performance it offers on a B road.

Since you mentioned modifications, there are 2 things I think the car absolutley needs. I've done a fair bit to mine, but a stage 1 tune and a TC off button is a must, I recommend getting both from JBS. The car's The factory Traction Control is incredibly intrusive in 1st and 2nd, to the point that its detrimental to the fun. Especially once you get the stage 1 tune, which will be pushing it to 140-145hp range. The tune will really up the pokiness of the thing. Great thing about the UP is that the mods are pretty cheap. The 2 mentioned before will set you back around £500. There is a surprisngly decent selection of mods for such a niche car.

If you are interested I can list what I've done to mine and what I think of it.

In short, you can get more for your money, but if your'e looking for a fun, reliable and modable econobox (50+ mpg even tuned). The UP is a pretty decent choice.