As far as buying from overseas is concerned and you are unable to get someone you already trust to check out the bike Your post makes me think of this: Do all you can to minimise the risks!
Do your homework, find out as much as you can about the seller. If they check out as reliable and honest...
Build up a good level of communication with the seller.
Get alternative contact details like phone numbers, addresses.
Ask for loads of pictures.
Ask specific q's about certain bits/frame so you know exactly where you stand - No nasty surprises on opening the box, hopefully.
Photos from seller of bike in its box.. Well packed /on its way?
If seller is reluctant to do these things and doesn't see the risks from your point of view, then I'd walk away
You'll have buyer protection through the usual channels? but TRY to buy cheap as possible, so if there's issues & all else fails, you can recover the cash.
This list is sure to be added to by more experienced Rb'ers on their way in minute
Who wants to have a sale that ends in a dispute that needs negotiations across countries?
Hope this helps a bit.