Re: Oops Alfa-Bollard collision!
The white is probably just scratched clear coat, it turns white when you scratch the surface. You can buy "scratch away" from Halfords or somewhere for this. I had almost the exact same damage on a Audi A4 and I used the sratch removal paste followed by T-Cut and some good polish, you really had to look hard to spot it afterwards.
Don't use wet & dry unless you are planning to repaint as is it will remove too much material. If you do respray, buy the airbrush kit they sell in Halfords and get them to mix some paint. Use thinners to thin the paint and then put on some thin coats followed by clear coat. When you spray clear coat, do it all in one go as it will dry very quickly.
I am not an expert, but I have done quite a few of these small repairs now.