Surely you will never really know if the buyer originated from sedo if you have the domain parked elsewhere such as dan.com or have your own landing page, as the buyer may well end up finding the name on sedo but enquiring through a different avenue.
No sales but had a recent £350 offer on Sedo for a domain parked at Dan.com, also had a £150 offer for lures.uk on Sedo today, that's also parked at Dan