[MENTION=10886]ChrisR27[/MENTION] - 2L is enough, just about. I read plenty of threads that said 2L would be plenty, and most people only managed to fit about 1.8 in - but in my case it was literally only just enough. The oil settled millimeters below the fill hole level. The FUCHS came to £20 total for 2L, and then Redline stuff was about double.
I didn't end up doing the change myself, paid £30 to local mechanic, which sort of sucks because the labour was more than the parts, but at least I know it's been done right.