Asia-focused bank Standard Chartered (STAN.L) said the location of its headquarters is under constant review and a big increase in a tax on banks in Britain meant it was watching the situation closely. “At the moment it’s something we’re watching, we’re looking at, we’re thinking about, but at this point in time there’s no change in our position,” Andy Halford, Standard Chartered’s finance director, said. “Clearly the increase in the (bank levy) number this time is pretty significant,” Halford told reporters on Tuesday.