And they make such a deal of this? The Swede attorney/judge/whatever can take a plane and go in UK to talk to him, that would be simpler and quicker.
That isn't the way police forces operate on the whole. It is not hard for Assange to go to Stockholm himself - he can drive there in under 21 hours straight.
And how cars leave UK? As far as I know, there is no bridge. Does Eurostar transport cars? The Dover-Calais boats, if they still exist?
Eurostar transports cars... sat next to a British couple in the Hofbrauhaus in Munich who had driven from suburban London
