@ Iggy
Thank's for the concern, not to worry paid via paypal so I'm covered if it doesn't turn up. The guy seems genuine enough he's got a 100% feedback record and he's sold three identical machines this month with good feedback.
I'll need to check it out properly (if it arrives) and get my mate Ron who's an Apple service engineer to have a good look at it, as I reckon he might be putting them together himself having sold three this month already. As long as it arrives and works fine I'll be more than happy, if not ebay have always been very quick in returning my money if something goes wrong, just have to wait and see now... 
Sorry, I shouldn't have even questioned on this. I know you're sharp enough to have this covered. And its been pretty rare that for me to experience bad transactions (especially with a seller with good feedback).
The only bad experience I've had recently was with a Radeon 9200 video card that I bought from a seller who offered a return policy. On plugging the card in, it damaged my motherboard.
After contacting the seller (who was PO'd that I'd posted negative feedback) I was inforfmed the card was untested and offered a return on the card.
Since postage back to the seller was higher than the cost of the card (and I was afraid he'd re-sell it to someone else) I took the loss. After all, the real loss was my motherboard.
I'm going to be really careful the next time I buy anything that could cause that kind of loss.
