rsjsouza
Thanks so much for taking your time to write and share your experience, indeed that was all I wanted to know. I had a look at the 513A and prices are slightly higher than 511 and 512, but that is not a concern. The most important is that I can rely, which you kindly told me about, on the tester and that it not cracks and goes into 1000 pieces in normal use. Of course it would be fine if it could stand a 3 meter drop.

What caught my eyes when I first saw these testers was the display and truly, that gets even better when I read about its accuracy - spot on. I like the size of the instrument, it doesn't necessarily have to be like an normal-DMM-size.
For sure there is times when more than 2,5kV is needed, so therefore I will go for, as you recommended, the 513A. I have a few projects running that might need higher voltages, but first out will be a insulation integrity test in our house.
Thanks again rsjsouza for taking your time to write a detailed feedback including your experience with the UT513