Well im sorry to say, you've put me off, gutted! the 250 is just too thirsty for my miles. I brought a MAzda 6 2.2 instead and so far after 300 miles im averaging at 55mpg.
In terms of sat navs, i do agree phones are better, i just like the aesthetics of a built in one. My old vauxhall vectra had a awful looking sat nav in it, no post code entry so was bit crap on A roads but the traffic alerts were better than most phone apps ive tried. Each to their own i guess.