Really just echoing most of above here.
I am actually looking for a new motor, and would happily consider a 3.2 A3. But I'll tell you what puts me off it.
For starters, its the twin grill front. I personally would only be interested in the single grill front as it freshens the look up no end (I have had a twin grill 8P before).
3 doors (this is obviously personal choice, but having had a 3 dr last time, I would much prefer a sportback).
They are the things that put me off, and there is nothing you can do about them in all honesty. Apart from that, I think its a pretty good ad, and has pretty much the spec I would want. So the thing that is holding you back is the price really. You are asking too much when these are going for less.
Black wheels wouldn't put me off, if they were the right size. But standard issue 16's / 17's in black would. To me it suggests you didn't have the money for 18"/19" wheels, and if you didn't have the money for that, what else would you not have the money for?
If it was me selling, as said previously, get her all nicely polished up, then waxed, and out into some scenery with a decent camera. It doesn't necessarily need to be on a hilltop with a view, although that wouldn't hurt. But even a nice urban setting can make all the difference.
So with completely new pictures, completely change the ad, different wording, emphasise the interior, make mention of running costs, like the actual mpg you get, as well as how it isn't the scary 450 quid for tax. Its amazing how soooo many people think that applies to motors such as this. Don't mention previous owner proffessions, but the low number of owners isn't going against it certainly.
Wouldn't mention horsepower, or "flappy paddle" myself, just DSG gearbox is enough. I would mention the light scuffs or other parts that annoy you, as honesty always helps with these things in my opinion. Bin the first to see will.... trap. NEVER use the word immaculate. Your immaculate and my immaculate are likely to be different. I also wouldn't add all the detail about things that are taken for granted as standard on these cars. ABS, power steering, window wipers etc... Unnecessary. And spellcheck the ad.
That should all help. But realistically, the reason it hasn't sold so far, is that its not priced competitivley, despit being well specced and low miles. If you are putting it back on ebay, 1p start, 3500 reserve. If you make more than the reserve, bonus. If you don't, it still doesn't sell. Simples.