Daz,
205/45X17 are quite a bit bigger in diameter compared to 195/55X15 and you'd need to check they'll fit both the front and rear arches.
FYI:- 195/50X15 = diameter 22.68inch/576mm
205/45X17 = diameter 24.26inch/616mm
difference in diameter = 6.94%/ 40mm
HTH BV
