Having had the 'Diesel Additive Minimum Level' warning flash up on my dash (Peugeot 307 Dturbo: Sept. 2002, with about 87000 miles on the clock) , I took the car to my local Peugeot dealership for a fluid top up.I thought that it would be fairly straightforward, but was told that, 7 times out of ten, the associated ECU resets okay, but if it doesn't, a new one is needed. Of course, mine did not reset and a new one was installed. The total job cost about £260. I had also phoned another local Peugeot dealership for a price for the same job and was quoted £400 to £450, so I suppose £260 wax not so bad. (The Particulate Filter was replaced about a year ago, at a cost of about £280.00, but apparently the fluid did not need filling at that time: I wonder, though, if it had been filled then, whether the total labour costs would have been less).
(as a matter of interest, I was given a 308, with the full glass roof, as a courtesy car - very nice!)