Hi Peter
I like you did a lot of recent on the model prior to buying, with at the forefront of my mind that's it's a mechanical item subject to all the variables that come with car ownership, overall reliability and build quality came out of my research time and time again.
I saw the steering rack issue on the American forums I think twice, water pumps simply weep but once replaced does not as far as my research takes me happen again, it's an improved design, in any event they do not simply fail.
If you can stretch to a car with warranty, it is a good warranty, and when I look at the issues with the RS/M3/C63 alternatives I was considering I have no doubt I made the right decision.
If you contact @Flytvr on here who has had the only rack issue he can tell you the details of how the fault manifests itself on the road, abling you to figure this into any road tests of cars that you find.
Good hunting
Big Rat