Coxy1, I´f been to many garages here in Denmark, and never seen anyone use a sump-pump. Might be different in UK & trend just hasnt reached us yet :-D
The big problem with the TDCI´s (should you guys not have heard about it), is that the oilpump sucks up oil from where the remains are, due to the fact the drainplug isnt in the lowest position of the sump. Offcourse it differs on diff. types of cars, but gravity likes to move stuff downwards, & with 5-5.5 ltr up through the pipe as Jabawok described, theres still 0,5-1 ltr left down there..Quite a big percentage, and 15% of this would be from 2 oilchanges ago..
Perhaps i overstated, and some engines wil run forever no matter what you do to them, but has seen guys just topping up on cars that used a bit of oil, killing those engines eventually...And statistically, you would/could see the same if you dont get it all out...If Alfa.Romeo get 6 liters out, the percentage remaining drops dramatically, but again, his procedure was written after my warning to the 5,5-6 ltrs. ;-)
Approx. 250 BHP (chipped) on a 2,4 Diesel is quite a lot & lubrication is a different story compared to the 2,5 ltr Peugeot 505 my parents had 30 years ago with like 82-84 BHP...It could prove to be some very expensive minutes to save for Jabawok not the get 1-1,4 ltr out of there, that was my point..Call it nonsense, if you like, i hope it is :-)