Both DVD & Blu-ray versions are being released as "stand-alone" units (i.e. Summer Wars on its own) or you can purhcase the "Double Pack" which features Summer Wars as well as another anime masterpiece "The Girl Who Leapt Through Time" film all in one box and at a very "competitive price".
As it stands if you want "The Girl Who Leapt Through Time" on Blu-ray you must buy the Summer Wars Combi-pack as the Girl Who Leapt Through Time will not be released as a stand-alone blu-ray until later on in the year, and even then it will still retail for around £14.99 - so if your planning on picking up Summer Wars, you might as well get the Combi Pack.
Summer Wars -> £12.85 (Zavvi UK) £12.93 (Amazon UK) £12.99 (HMV UK/Play UK)
Summer Wars & The Girl Who Leapt Through Time (Combi Pack) -> £17.85 (Zavvi UK) £17.93 (Amazon UK) £17.99 (HMV UK/Play UK)
The Girl Who Leapt Through Time: When 17-year-old Makoto Konno gains the ability to, quite literally, "leap" backwards through time, she immediately sets about improving her grades and preventing personal mishaps. However, she soon realises that changing the past isn't as simple as it seems, and eventually, will have to rely on her new powers to shape the future of herself and her friends.
Summer Wars: When timid eleventh-grader and math genius Kenji Koiso is asked by older student and secret crush Natsuki to come with her to her family's Nagano home for a summer job, he agrees without hesitation. Natsuki's family, the Jinnouchi clan, dates back to the Muromachi era, and they've all come together to celebrate the 90th birthday of the spunky matriarch of the family, Sakae. That's when Kenji discovers his "summer job" is to pretend to be Natsuki's fiancé and dance with her at the birthday celebration. As Kenji attempts to keep up with Natsuki's act around her family, he receives a strange math problem on his cell phone which, being a math genius, he can't resist solving. As it turns out, the solution to the mysterious equation causes a hijacking of the social networking site through which most of the world's social and business traffic flows. It's up to Kenji and his new fake family to put reality back in order.