205/55 is really a bit oversized ... about 5% too big; but if you want to get your money's worth out of the tyres it's not going to hurt anything. Just keep in mind that you'll be doing 105kph when your speedo reads 100.
Ideally, you'd want to go for 195/50, which is only 0.3% undersize, or if you want to stick with the fatter profile, 205/50's are only 1.4% oversize.