I presume you have a 100hp with 195/45 R15's?
You'll gain 9.75mm of ride height with the 50's over the 45's.
The 50 or 45 in the tyre figure is % of the width not total height in millimeters.
So it's height is 50% of 195mm (97.5mm) compared to 45% of 195mm (87.75mm)
You'll also lose 9.75mm of wheel arch gap.
If the taller tyres don't catch on anything, it may look ungainly on such tall tyres.
Diameter will go from 556.5mm to 576mm, so you will lose a little acceleration as you're gearing it up slightly, but saying that, at cruise it will pull slightly less rpm.
Your speedo will read -3.39%
So reading 30mph you'll be doing 28.98mph, 60mph and you'll be doing 57.97mph.