It turns out, perusing the iTunes Store this evening, that the BBC Worldwide content has already appeared. Shows initially showing up include Torchwood, Spooks, The Mighty Boosh, Life on Mars, The Catherine Tate Show, Two Pints of Lager and a Packet of Crisps and finally Little Britain. All the episodes cost the regular UK pricing of £1.89 and currently, there's just a selection of series available: Spooks (known in the US as MI:5) is showing just Series 6 currently.
At least for now, the shows appear to be UK-only. Updated: shows will be available to download and buy 8 days after broadcast.