Iv got a '09 plate pd 170, with just shy of 36kmiles on, I average 43 mpg around the doors and commute to work daily ( 14 mile round trip). The wife can get anywhere from 36 to 39mpg but I don't think she s found 6th gear, I use the cruise control quite a bit around town, don t think you'll have any problems with dpf if you do over 12kmiles a year any less I'd recommend a petrol
I went to Manchester airport from Gateshead last weekend to pick my mother up and averaged 53mpg @ 70mph, I managed 301mile out £40 diesel. I think I might be able to push high 500 to 600mile out of a tank,
Diesel is great for economy,and is punchy around town,but its not for me, I'll be hoping to get back into a petrol soon