>> Is there a way to turn off the lines, apart from picking them out one by one and hitting the hide button?

Hi Fraser,

After you've selected one line, just press CTRL-A (or the Select All button in the Select pane). This will select all the remaining lines (provided that all your surfaces are joined together...)
If the curves you want to hide are on different objects, you must select a curve on first object, then you can select other (full) objects and finally select curves on them.

By the way, Michael, is it normal (!) that if you have several non joined surfaces (or different objects) and that you select a curve on one of them and press CTRL-A, MoI will highlight all curves on the selected surface and all the other surfaces, not the curves ???
Maybe not a bug, but at least some "unexpected" behaviour...