Well, it didn't exactly leave much room for napping. He found himself overtired more often than not, and today was especially harsh, as he was now dealing with a hangover so massive, it put all others to shame. And, as much as he wanted to crash and burn for a few hours in his room, he knew that Sherlock would be along soon enough to draw him out on another adventure. So, when the Welsh bloke - Ianto, he figured, because it was the name that stood out as the most Welsh in his memory - offered an escape route, John had leaped at the chance.
So, there he was, having dug around to find someone to take him to Cardiff - though, was it even the same Cardiff as he was used to? He'd told them who he wanted to see, and that's where he'd been taken, so. Only time would tell if this was his world or not. (And how strange it was to take that concept at face value!) Now, in the Plass - he'd been to Cardiff once, a long time ago, so it was practically like new - John dug out his phone and opened a text to the number he'd by now stored in his address book.
...Right, this wasn't Sherlock he was dealing with. He could call. Rolling his eyes at his own idiocy, he sent a call to Ianto to let him know he was by the (obnoxious? a little) fountain in the center. After all, it was the easiest landmark to be noticed by.