If yours is a MK4 1.2 it'll be fine... most people jump up a few inches when upgrading alloys.
Its the depth of the tyre that you have to watch when going up a few inches.
They are 6.5J ET42, standard Ibiza Sport wheels are ET43. Your steels are either 5J ET35 or 6J ET43
Would it be hard to adapt them? I think it would suit the car well and not look over the top. A first on a MK4 too?