Finally sorted this out. Easy enough job but a bit of a pain in the ass without a garage/driveway. Got there in the end though and cleared the WOF so mission accomplished.
Huge thanks to @Eagle for sending me that steering coupler, was a huge help.
Sounds like the 6cyl diesel would be the one to get. We have a 530d F10 and it’s been great; i’d take it over any of the F10 petrols.
Go test drive an F31 330/335d .