ANN notes that the first two films will both be screened as part of Philadelphia's Cinefest, which runs March 26 to April 6. There are no DVD release plans in North America yet, so if you get a chance to catch a screening, I highly recommend attending if you can. The first film was among Japan's top-grossing domestic pics for 2008 and the second film just opened there in January.
As for you fans in the UK, you'll have your shot at the first film, at least; Anime UK reports that the ICA (Institute of Contemporary Arts) in London is screening the first film from now until Wednesday. So if you want to catch it, you'd better make it soon!