So how are they going to get Julian Assange out of England?

[exboyfil]

14. Very large diplomatic pouch

Any restricitons on the size?

It has happened at least twice according to Wikipedia.

In 1964, a Moroccan-born Israeli double agent named Mordechai Ben Masoud Louk (also known as Josef Dahan) was drugged, bound, and placed in a diplomatic bag at the Egyptian Embassy in Rome, but was rescued by the Italians.[4] The crate that he had been placed in appeared to have been used for a similar purpose before, possibly for an Egyptian military official who had defected to Italy several years before but then disappeared without a trace before reappearing under Egyptian custody and facing trial.

In the 1984 Dikko Affair, a former Nigerian government minister, was kidnapped and placed in a shipping crate, in an attempt to transport him from the United Kingdom back to Nigeria for trial.[4] However, it was not marked as a diplomatic bag, which allowed British customs to open it.[4]