Changing timing belt but not the water pump

Is water pump run off the TB in that engine or independently mechanically operated

The water pump is separate on that engine. It’s not ran off the timing belt, it’s on the other side of the engine.

It’s recommended to change water pumps that are driven off the timing belt in case it seizes and destroys the belt, which won’t happen on that engine.

I had the water pump replaced on a 2017 1.2 tsi golf recently, which is how I know.
presuming it’s the same on an Ibiza.

The other reason you do both (on a timing belt driven pump) at the same time is that you have 90% of the job done when the timing belt is off so there is little extra cost other than the component to do the pump at the same time.