I changed my rear tyres from 215/45 to 205/45 as I needed more space for fender clearence.
Sidenote: Originally I was planning 205/45 as well but the PZero I put on the 8" had too much strech for my taste so I upgraded to 215. As PZeros are not available in 215 I bought a pair of new Conti Premium2s that seemed to be at least 225s or so when monted! Long story short I found that Contis are more robust, while Pirellis are more narrow than any other tyres in the same size. Finally I choose Michelin PilotSport3, it is said to be a very good street tyre on low weight cars (MX-5, Clio Sport etc.) and the 205/45 fits perfectly for the 8 wide rims, exactly what I wanted at the beginning.
Continental:
Michelin:
