It just seems mighty fishy that his sister was so quick with the nonsensical 'she threw herself at him' defence and the additional satnav detail.
Something made the police arrest this guy. His car matches the one in cobweb cctv (doesn't it?), it was parked 10m away from where Libby was last seen and it appears that a woman wearing a skirt and short jacket got into it.
I think I agree with a previous poster who suggested the police charged him with the knicker stealing/flashing/burgling stuff just to get him into custody. He may not be the flasher, but they don't care, as long as they've got him under their control, because perhaps they see him as a flight risk.
It does appear that the passenger is holding a lit up mobile phone, which presumably belongs to the driver. It would make sense that he got her to put her address into his phone if he's pretending to be a kosher cab driver (i.e. he has to have a record of his movements or whatever). If we're right and she had no way of getting into her house, the only address that makes sense for her to input is the Welly, so she could get hold of her friends. So if he drove her back to the Welly, she'd be confident he's going the right way... until he then veers off to Pearson Park. He could have done something terrible to her there, left her and what with the freezing temperatures... I don't want to end the sentence.