LR3 Idle Fluctuates w/ AC on or off - please Help ASAP- Looking to Buy this LR3

I'm looking to buy a 05 LR3, just did a test drive today and noticed the idle fluctuates, even after the engine is warm. The problem gets worse once the AC compressor kicks on.
i couldn't hear any high pitched squealing and the AC compressor was replaced in late 08'.
I recorded a video of the idle which you can see fluctuates from :

http://youtu.be/jZzC5fCdQRE

500-750rpm without the AC on
400-1000rpm WITH the AC on - dropping down to 300rpms almost stalling if I rev it a little (as shown at 1:05mins)

<iframe width="560" height="315" src="//www.youtube.com/embed/jZzC5fCdQRE?rel=0" frameborder="0" allowfullscreen></iframe>

this obviously seems not normal.

MY QUESTION: Does anyone have any idea as to what could potentially be wrong (and cost if possible)? I do a lot of work myself but unsure in this scenario. Basically, the price of the car is a great deal and they are willing to knock off about $700-800 more due to this issue...However I'm worried it might be a bigger issue.

All thoughts are welcome and the sooner the better! Thanks
Land Rover LR3 2005 SE 4.4L 83Kmiles

Easy fix, don't hesitate on purchase for this at all.

Have an induction service preformed, and replace the PCV valve afterwards, along with an oil change. At that mileage, might want to have a proper injection service and full tune up as well, it will run much better after.

The symptom is due to carbon fouling on the throttle blade. This symptom can be removed by just cleaning the throttle(manual cleaning with a rag is not recommended), but to properly clean the intake system, and prevent it from fouling again quickly, do as above. Not sure if I can link other forums on here, but I have done a few write ups and full explanations before, both on landroverforums and rangerovers .net. Search for induction and you should find a few good threads.

Here's a helpful video for the Throttle Body

Discovery LR3 - Cleaning Throttle Body - YouTube

Thanks guys...Great info and I appreciate the quick reply!

+3. 20 minute fix and free!, provided you can get a hold of good solvents.
That's about the same mileage mine needed it as well.