You need a 22" (550mm) for the drivers side.
And a 21" (530mm) for the passenger side.
The best blades are the Bosch Aero type.
Not only are they smear free but they divert flies, crud and light drizzle up over the windscreen. And they last much longer.
Bosch do a special set of 2 called Aerotwin for LandRover, M-Benz, and Rover 75s which use this staggered size.
The code number you need is AeroTwin AR550S which comes with one of each size in the box.
Cost just under £19 on ebay -there are other suppliers - like 'Wiper Blades Ltd. of Kidderminster for example - very quick - next day delivery.