I've just fitted a set of Bosch Aerotwin retro-fit blades to my car, £17 off eBay, and I think they look great! They don't seem to stick up as much as the other pictures people have shown so I'm not sure if it's because they weren't Bosch ones or something
21" and 19" and they seem to fit fine. I compared them to the standard wipers and the lengths were more or less the same. The only thing is the passenger side wiper doesn't quite sit flat on the 2-3" of the screen near the tax disc but once they move from the rest position it makes full contact with the screen.
Standard wipers:
One standard one Aerotwin:
Aerotwins:
Outside view: