That's the RS200 that Stav was referring to. The trim spec can vary, see this website for a guide.
Imports can be more expensive to insure, but then again you can try specialists like Sky Insurance (trader on here) that are used to that sort of thing.
I think that a lot of the parts are common and will be easy to get via Toyota/Lexus. Don't know how easy it is to get the Altezza-specific parts.
As Stav said, try using the "Search" button on the forum to look for "Altezza"