Your inbox is full mate!
Here's what I tried to send you:
If you're doing an aftermarket system then it's meant to work well by flattening out the eq. The normal base head unit is apparently coded to compensate for the oem speakers so it makes sense to flatten it out if you're putting an amp and speakers in there. One thing tho, apparently coding to HiFi changes the output to a balanced differential output rather than line or speaker level so you need to bear this in mind either with an amp that can take bd or with converters.
As for location, I'm about 18 miles south of Peterborough. Give us a shout and we can try and arrange something!
MY14 Space Grey F11 530d M-Sport