I'm sorry for my ignorance, but the above statement is coming from a person who has put too much blind faith into the capabilities of BMW tech. I'm apologize but BMW mechanics tend to be heavily pre-programmed to associate any issue with electrical troubles and forgetting the essentials of repairing a vehicle. Nonetheless, I would attempt to document all the codes you have received, it may help us help u better.
The active steerin component is hydraulic. However the active steering system does change the ratio based on engine speed and vehicle speed. However i don't see an electrical connection beside sps. I would also think its got to be a faulty mechanical pump of sorts, since according to your account they replaced and diagnosed alOt of electrical systems involved with the steering.
It's disappointing that the uk doesn't have consumer purchase protection laws in regards to vehicle mfg defects.
BMW and Mercedes Build Beta Products!
Lexus build Release Candidate Products!
Why does this matter?
CAUSE EVERY TIME someone says Lexus has better build quality, one should consider what Toyota their Lexus Engine and chassis platform comes out of and how long that part has been tested in the real world!