Which option depends on what you want to achieve
If you are looking for what will help residuals / resale then min extras should be.
Air con (manual is fine - all cars will have this soon)
Salt or pepper pack (bright interior, external chrome - most will have it and if yours does not it will stand out)
CD player (either multi changer on the std radio or CD boost, ideally radio boost and CD but thats a lot of dosh)
Leather steering wheel and gear knob (instant sex appeal when you hold the wheel - the buyers already got a grin on their face and you haven't given them the keys yet)
Colour is important too. Of the solid colours red and black are safe. Avoid yellow (I'm going to get killed for that). Metallic tends to be best but lots of people think green is unlucky (inc. my wife and I wanted BRG). Safest is silver, classy, timeless, suits the cooper, I'm biased cos mine is pure silver
Thats all you need, other bits are cool but when it comes to appealling to the biggest market that's all you need.
If you want it to look great then the 16 inch wheels are a must (not that it doesn't look great in basic trim cos is does) but it just adds that sexy bad boy (or girl) look that a fiesta or a corsa couldn't manage in a million years
If it's a cooper then the chilli pack is great value and the 16 inch wheels and roof spoiler look fantastic. I've seen posts where people are unsure about the SSP. It's a Mini Cooper !!! It's supposed to handle like a go cart. If you want a comfy ride buy a mini one, safe 2 grand on the basic price and then blow it on options.
For what it's worth I've got ASC and I love it. Damp road, traffic light grand prix with a sporty renault clio, bend, bumpy road, neck and neck, hit bumps, traction light flashes, clio history, huge grin
