Russ
Alexa and the like help a little but not much...
If I were buying a name for serious money, I'd want to see it on Sedo so I can see sedo's traffic data... THEN, I'd call sedo and ask them to verify too... Just my way BUT, it's the only way anyone would get 'serious' £xxx + from me, unless I knew they were honourable...
Their are members on here who are totally trustworthy... From whom, I wouldn't hesitate to buy...
Take a look at domain trader ratings OR their level of commitment on the forum...
None of the 'acorn stalwarts' are gonna rip you as it would be stupid to do so...
Like Grant has said, they wouldn't last long... Certainly not here...