I started selling on 18 Jan with the 10 limit, and sold 8.

On Feb 2, I rang ebay to ask when the limit reset, because I wanted to list another 10 for Feb, and she told me, but (unprompted) said not to worry, she was going to increase the limit to 100, which she did.

On March 2 I rang and asked for an increase, and they increased it to 200; that was the only increase I actually asked for.

Subsequently, during March and April I got 3 of those unprompted emails you mentioned, increasing it to 320, then 470, then 570.