First tank done. 508 miles, 35.6 MPG. This was a mixture of trips to London, short (7 mile) school runs and my 30 mile each way commute. On the commute I don't cane it (no point), but I stick at about 70 on the motorway. All in all, I'm pretty happy as I wasn't exactly shy about using the stupendous torque to nail a fair number of dawdlers.
The car is a 2008 2.4 Sportwagon, remapped and DPF removed by AHM.
For slowing down to light, roundabouts your better of sticking it in the highest gear, and taking your foot off the accelerator, if you knock it out of gear it uses fuel to stop the engine stalling.
Surely it depends on the situation. If you're coming in way too fast, then yes, sticking it in 6th will bleed off speed and cost nothing in diesel. If you've timed it to perfection, then you don't want engine braking, and you just coast in. You use a bit more diesel in the coasting phase, but you saved far more earlier by not accelerating.
Overall, I'm pretty happy. The 159 can't tow a 3 tonne trailer like the Land Rover, but the Landrover would regularly do 200 miles on a tank that is about the same size as the 159s.....!