My '98 LS400 had the original CD.
I got the latest available in 2006 from Lexus Newcastle and it cost me £161, but I'm not sure what the version number was.
When you load the disc it takes a while because it upgrades the application software as well as the maps. Be patient.
I think one of the updates is house numbers, which you couldn't enter on the previous version.
Maps are good, and the whole of UK is covered, but the York by-pass is not. You'll be back in that field.
I've no complaints. Well worth the money to me.