Single width garage ? - Folding mirrors yes, the cost is the same as repairing a scuff or two
Rear parking sensors - might save a parking scuff, cost less than a new bumper
Front park sensors ? - deabatable, can't see the point myself
Park Assist - fine for city dwellers who parallel park a lot, but for townie use a waste and not foolproof either
Winter pack - yes in Scotland
ACC - all depends on what you want the ride to be like, 18s and the sports suspension are pretty firm, but some like it like that, others not so. You'll be dodging potholes on less well maintanied roads. ACC won't save a rim of course, but it might make the car less susceptible to mid corner bumps and will offer a slightly more comfotable ride. All down to personal choice on ride firmness and what any passengers will like/dislike
Audio - again its personal thing, some people listen to a lot of music, others don't bother. Dynaudio is quite impressive upgrade, but not everyone is bothered, and audio in a car is compromised and not 'hi-fi' anyway. Remember your ipod/usb is a compressed audio format anyway !
Leather - its cold in winter and slippy on hard cornering, cloth seats are a lot better on either count. WEar on the bolsters might be an issue for long term ownership, but leather would crack n split in that area anyway.
Sat nav - if you have bottomless pockets, a £300 Tomtom is far superior
Sunroof - adds weight in the worst place for handling, pointless IMHO
Xenons - lots of dark wet roads at highish speed, where you can't use main beam due to other road users,. then yes albeit you pay handsomely. More driving on illuminated roads, or town use then save your money.
Storage - not exactly commodious drawers under the seats, but useful additional storage pockets given the lack in rest of cabin.