Ok, yes you really should test drive the car.
Although its difficult to get the feel of the thing first time out you can pick up on basic stuff like steering and clutch/gearbox etc. Also the possibility of bad clonks and groans which sound expensive.
Why don’t you phone them up and say you been thinking about it and feel you want to drive the car BEFORE you hand over the cash. It’s a reasonable request and I cant see them deny it. If they refuse walk away quickly.
Its not only problems with the car but how you get on with it. I think the
Ibiza is pretty easy to drive so should not be a
problem but everyone is different. For example when my girlfriend bought her Mini Cooper I sat in it and loved it but when i drove one i could not find a truly comfortable driving position (still cant) and would not have chosen it myself.
The only time I did not test drive a car was when it was a family member and they were practically giving it to me so it was not polite. That car was fine though.