Was the first a large auction house? I'm bemused by the need to register with auctionet afterwards. How difficult is it to have someone take card payments over the phone, particularly as you presumably were able to bid without doing so? Sounds overly complicated!
?? Surely, buyer's premium is added to the hammer cost. So it's something that I do have to pay (plus vat) as a buyer. And take into consideration when bidding.
I also bear it in mind when reviewing what level of 'service' I feel I've received, such as speed and cost of dispatch and the level of care taken to safely package my purchases. That the seller might not get as much because everyone is adjusting their bids down by 30% is of course also an issue.