Given you have an 11 plate and he's after an 09 for 6k, quite a lot.
The new Astra is night and day better than the old one.
If the new one is night and day better than the old one, then the old one must be awful. I had a 62 plate 2.0 CDTi last weekend. Covered around 500miles in it. I didn't get on with it at all. One of my main bug bears with it was that everything felt like separated. I'll try and explain what I mean by that.
On the dash there are two screens, one in the centre above the radio and one in between the rev counter and speedometer. Fairly standard setup. Both of these screens were low res bright orange dot matrix screens. Neither offered much information and nor did they work with each other. The centre screen felt very much like the 'radio' and the other screen was about the way the car was running. Changing the fan speed meant that you got a full screen child's drawing of a fan with a number next to it on the radio screen - that bugged me it hung around for ages.
When you activated the cruise control, it was just 'on'. With + / - buttons the steering wheel to adjust it. No confirmation of the speed you'd actually set it to, or what you were adjusting it to. You just had to up/down it and wait and see.
To change options on the screens, you need to use a cheap feeling spring loaded twisty toggle thing; and flicking through these option gave you ONE piece of information per 'page'. MPG, range, speed etc - all on separate pages. When you've got a screen the size of the Astra DO MORE WITH IT!!
Placement of controls on the dash was also an annoyance. On the radio, there is a large knob in the middle of it and a smaller one above it. You've expect that the larger one would handle the most commonly requested function on a radio - volume change. It doesn't, it's the manual tuning. The smaller one is volume. WHY.
The back lighting on the screen is adjusted by a scroll wheel that is next to the headlight switch. That annoyed me. I expected it to be in the options for the 'screen' - or at least in a place that I could see whilst driving, seeing as though I'm likely to want to adjust it whilst driving. But no, it's not visible to the driver whilst driving unless you shuffle over to one side and move your head down.
Speaking of driving positions, didn't like that either. The whole dash area felt like it had been squished up, the steering wheel hid many of the dash readouts and despite adjusting the steering wheel and my seat I never got it 'right'.
At night, there are red lights dotted around the interior to light things up. The doors have them in the handles. I couldn't tell if they were meant to be lighting the electric window switches (why, they glow anyway), the door handles (not the bit that opens the door, the bit you pull when closing the door) or the door bins. Either way, they looked naff and were not needed.
The seats were not particularly comfortable. The climate control was either too hot or too cold, with rapid swings from one to the other.
The engine was noisy and felt like it stalled everytime the stop/start kicked in at traffic lights. It, without fail, kind of juddered as it stopped.
Despite the noise, the engine was alright. iirC 165ps. So it'd shift a bit if you put your foot down (assuming the whining turbo had spooled up and you hadn't gone too far up the rev range yet!). It wasn't great on fuel, but it didn't feel short of power either.
I do feel like I'd been a bit harsh on the Astra, but I am stuck comparing it to the car which I had the previous weekend; 508 SW. Which was just a much better car in almost every respect. All my moans about the screens, the instruments, the cruise control etc were all none issues in the 508. The Astra was a faster car though. My missus didn't like it as much, but that was purely down to the looks of the 508 and the fact it was an estate.