Think I'm quite late here. You probably have bought her already. If so, Congratulations! She's one of a kind
Anyway, I bought a 2003 manual CS3 about a month back for 18.5M. I also thought the appropriate price should be 18M, but went for +50K since it has done only 78000km and everything was in excellent condition - that car had been rarely used. Did a full check up by the professionals before buying.
At that time there were 2003 CS3s from about 16M-18M, if I recall correctly. Ones for 16M was abused And many had done more than 150,000KM. Some even 200,000+