a little update with my situation.
I have a 120i coupe and since march, after it has been sitting for a couple hours, it will struggle to start up and cranks/turns over a lot.
Took it to BMW Sytner, 1st time they said there were no codes and could not fault it. 2nd time they changed the "fuel sensor" but the problem continued to happen. 3rd time they changed the "high pressure fuel pump" (even though I was told that this model does not have 1!) but AGAIN the problem is still happening.
Getting sick and tired with BMW now.