Sadly I only have Lightroom, although I do believe you can do the same in there. The trouble is that it's usually on the cusp of the horizon, so clone works better than heal some times, depending on the angle of the shot. Not being a circle, it's not the easiest thing to subtly remove with the limited tools in lightroom.
Come to think of it, I suspect it is actually on the sensor, just that the other main lens (which doesn't seem to exhibit the issue) is rarely used stopped down very far. I seem to remember reading you notice more dirt the smaller the aperture, however if that's correct is another matter. I'm somewhat averse however to poking (however gently) the expensive bit of my £2000 toy, so I may take it somewhere to be done properly. It may even have shaken itself off by now…