John, thanks for that info I'll go and look at that post in a mo!
Lance,I bought a kit. It contains 4.5 Litres of additive, some fancy pipework with a tap etc.to put it in with and a 1 Litre bottle for the waste fluid. The kit price was 71.35+vat retail, which is still expensive but better than 24 quid a Litre. The part number I bought is 997995 but be careful as there is more than one type of fluid, they asked me the filler cap colour!(unless of course the kit has different filler couplings) The filler cap on a 607 is just in front of the nearside rear wheel, sticking out of the side of the tank which is on the leftside of the diesel tank.HTH and thanks Shaun.