The Porto Grande offers a huge and excellent anchorage. We first went over to the east side, and anchored in 8m. This was gooey, soft mud, and it took the rocna a surprisingly long time to bite. We looked around at the industrial landscape and the mucky brown water and decided to up sticks and be close to harbour front.
So we meandered back through the 20 or so boats (Czech, French, American) and ended up the nearest to the front. It's a stunning view, and not too disrupted by passing wake. The water is cleaner here too.
You can tie up, stern/bows to using your own anchor, for free on the Grand Harbour. We decided not to bother. It's much hotter, there's the risk of cousins of Maurice of course, and there is less security. But if one wanted to be alongside for any reason, this would be an acceptable free spot. There are also two marinas, one each side or Orytega.sp
Update, 2 days later: Just as we were writing this, the Coast Guard turned up and made us move, indicating that we should move west beyond the commercial dock. So after two days enjoying the view, we are back nearly where we started. We aren't wholly surprised as we were quite close, but then, they didn't move us for all the celebrations. Still, the water is now cleaner, and there isn't any water-borne industrial traffic and the shelter from the forecast northerlies is better here.
Update, yet another day later: we found why they'd moved us when two huge cruise liners turned up: we would have been right in the way.