Sorry folks for the mix-up from early May. When news arose one month ago about a
new Gainax anime set in early 1900s England, and then just days later they
announced an anime called
Panty & Stocking with Garterbelt, it seemed only natural to assume that they were one and the same project (contradicting as the themes were). But as it turns out, they're two different things.

Speaking at the "History of Gainax" panel at FanimeCon 2010 in San Jose, California over the weekend, the anime studio's co-founder and executive director Hiroyuki Yamaga
confirmed that, aside from Panty & Stocking, they're also working on another, "more refined" anime - and that this was, in fact, the one set in early 20th century England (between 1900 and 1930, according to the studio's earlier job listing).
Of course, that still leaves a heap of questions to be answered, and probably raises a few more on top. Not to mention that at last year's FanimeCon, it was the same Yamaga who
announced another couple of anime projects - different from this year's confusing duo - which have yet to materialize, as far as I know.