Maybe they have but laws over there are different and the police haven't been bothered from day 1, I doubt they'd want to and they certainly wouldn't want to go through all the process of getting a warrant. I don't believe they did it, if they did why are they still so intent on keeping her in the press and getting leads and things, and they got cleared by Scotland Yard anyway. They probably don't push it because that is one lead, there has been loads more leads leading to her still being alive (sightings of a girl who looked the same in a car on a campsite that the girl wasn't in their original booking didnt talk looked drugged and didn't look at all with the family, as well as possible sightings of her in other countries since much more recently), which over the 2, I'd rather believe the many leads of her still being alive.
If they had of done it they'd be wanting to keep the attention away from them, not keep drawing it to themselves and her. I'll admit I had my suspicions about them in the past, but I honestly don't think they did it now.
The pictures on the link OP posted if you go on gallery at the bottom they're on there.x