The rears on mine barely got used so I stuck with standard, but I guess you could use something like an RC5 pad if you feel you need to splash the extra cash.
For the rear just use the standard pad they're more than adequate. Rears hardly do any effort.
For the fronts standard pads are adequate, a decent upgrade is Ferodo DS2500. Ive just got some to go on the front of my 197 Cup (same brakes as your Meggy)