Regarding the comments on the Skoda Fabia bolting - still accelerating when foot off clutch and accelerator, I don't agree with Matt's comments that this is normal. After noticing that my Skoda Fabia does this, I did some tests on it when driving. Finding a long empty road, I went up to top gear then took my foot off clutch and accelerator to see what would happen. The car initially slows down, then when it slows to about 25 mph, it judders, then starts accelerating again, leveling out at about 35mph. I have driven for 7 miles like this, both feet off pedals. I have also tried it on uphill roads, and does the same. It just cannot be normal for a car to accelerate UPHILL with feet off pedals. I don't know how long this would continue for, as junctions, lights, other cars have stopped the test, but it seems it would just carry on. Sorry but "long gears" notwithstanding (whatever that means!!) this is just not normal, and I would love someone to tell me why it happens.
This is 100% normal, my Nissan Almera does it, my Skoda Octavia did it, and not just in top gear. In traffic I can crawl along (including up hills) at 5+ mph with both feet off the pedals quite happily.
If your car is modern TDI version of the Fabia, I would guess that the final drive ratio is something like 35mph/1000revs, so really, that's what it's geared at. Idle speed is approx 8-900 revs, so the car is probably crawling along at virtually idle. There's a lot of torque so the car continues to do this even uphill. Every car will do this to a certain extent, but a petrol would probably just stall.
I would say this is normal for your vehicle. I have a Focus TDI, and I think mine would do it too (to a certain extent).