OK, bad news, but thanks.
I could'nt find the earlier discussion thread.
Having checked a few other brands, only HB seems to do this. I asume that its a market protection issue, discouraging importation of US units to countries where HB distributors are having higher cost structures (i.e. typically charging 2 x that of the US).
On the technical side, presumably Humminbird could make the software work around the firmware if they wanted to.
Greg