Hi I'm from the UK. I've just taken delivery of my first ever Diesel.
(Audi A3 2.0 Litre TDI,
I've just did a test of my own. And yeah I do recommend BP Ultimate Diesel (Centene Level 57/58). It does quiet it down a little and this is noticable. Performance wise it feels more better in pulling power. It's almost Petrol like in some cases.
Previously I tried a little supermarket stuff at my local Tesco's (Cetene Level 51)... Never again! It sounded like a truck most of the time!
Shell are due to release "Diesel Extra", it's widely available up north in England. But is slowly being available to us Southerners. Closest I've seen is Letchworth in Hertfordshire so far (2004). But BP Ultimate Diesel is already beaten the race to get down south.