Hi Dest, (its Craig!)
welcome!
ive not been here long, but hopefully am able to answer a couple of your questions.
regarding the seats, it needs to be an Msport you go for, as the SE seats are pretty horrible imo (i have them
). The standard msports have cloth centre with alacantara bolsters, personally id want leather, but the stock msports are nice too.
Pan roof is Tourings only
Idrive is nice, however i'm under the impression that all but the very latest "CiC" iDrive is surpassed by a decent double din unit like yours. you can get a double din fascia and it just bolts in, you get looms to keep steering wheel functionality as well.
i take it your manual requirements are the reason for avoiding the 335D, and i guess i would agree with you, the 330D's ain't no slouch when remapped (obviously not RS4 pace, but brisk enough)
i reckon you would easily be able to swap out the leather for stock msport seats easily, prob get cash your way as well.