Melita, Simon,
the only real use for those, so called, "Lo" projection definitions in the Arc software is to be able to define certain "upside down" CAD files that you come across quite frequently here in SA. If you preview one of these in Catalog, generally you can see a north arrow pointing down and the extents will show a +ve Y value.
Then all you need is the zone number (17, 19, 21 etc).
But I wish esri had not named these things "Lo", cos its not. Should have called it "pseudo Lo" or something.
In reality, "Lo" is southward facing and axes swopped (X increases from N to S & Y increases from E to W) and is not supported in anything software I know about. How could it be?
Most people just convert single point coords back to a normal, right way up TM (X is Y and Y is X and both are multiplied by -1).