There isn't a plate diff for the Ibiza only a ATB and trust me you know the differeance! I love mine..... going by it's a ATB you will feel it lock in when it's needed and pulling the steering at 1st.
If you put the handbrake up it wouldn't really stop one front wheel them spinning, once the wheels loose traction they will continue to spin. And I found since I've had my ATB diff fitted the gearbox is a lot louder than a standard one.
Ah! I would check more details on that Dave. He is using an 020 box for which you can deffo get a plate diff. I have had both gripper and kaaz in mine. Also had the quaife atb and they are pretty good but you loose time as you loose traction when you unload a wheel in a corner. You can also get kaaz plated diffs for the 02A which comes in the 16v, also plenty of other plate diffs on the market for the 02A available in Germany and USA. Check out www.bildon.com They have a good selection on there.