Antwerpen is a beautiful city in Belgium with the biggest train station in Europe. But for us the athmosephere wasn't the best and we couldn't enjoy it that much
The same as in Leuven. You have to get a paper for free from the city hall witch contains the rules for street music/street performances. But again the police didn't really care that much, and if you are polite nothing bad can happen.
First we tried the big shopping streets which starst from the Central Station and goes towards to the center. It's really crowded and people seem not to care too much about street music. It's a really noisy street also.(I have to mention a pianist who plays in Antwerp on the streets with a real! piano and he is quite good :)). So we couldn't find the right spot on that street. In the center there are too many terrases and we didn't want to play in front of them. We saw some musicians playing in front of a church gate and we gave it a try too, and it was quite good at the first time, second time it was quite bad... People just seemed a bit posh.
We stayed just for 3 days so we didn't find the right spot for us. We had bad luck.
Maybe if you are loud or you are with a band can be good :)