Entirely depends on quality, but for a "Decent" JZX100 you're looking at £20K plus. Better value for money is a JZS171 Crown (That I have for sale ) only think you're missing are the "JZX" scene points.
Honestly, for a nice example, there isn't a lot in it. My friend just sold his auto for 17K a few months back. It was a good example, but still, you're really not far off unless you want a beater in my opinion at least. Best of luck with the search none the less.
You'd be better off with a JZX110 IMO, unless you really want a Chaser. You can get an auto 110 for reasonable money.
I like the way they look, but regardless they aren't as ugly as everyone makes out. Some great advantages over the 100. They just aren't as 'scene' {}