I fitted a 40mm lowing kit by H&R ordered from larkspeed.
The ride is firmer that standard but not undriveable, not sure on the height from the ground but it does not scrape on speed bumps and clears curbs when parking.
As i have only had i lowered for a couple of days i have not yet noticed an improvement in fuel economy but hoping it will as i am achieving an average or 41mpg currently (hdi160)
I'm not planning any further mods as the ride height was the only think i did not like about the car.