It’s blind, best thing we did was list and sell ours before bids closed (12 hours to spare!!!!) with the same estate agents. because they were getting 2 sales (none of the other bidders were selling with them if at all) they might have been a but naughty and said something along the lines of “all bids are in, yours isn’t quite enough…” we upped 10k and we got it (40K over asking, was 3 now only 2 beds)
To this day I don’t know if they just rinsed us for 10k or not. I did feel a pang of guilt about it, but it was a rare opportunity for us to have any chance of buying in the area we wanted and most of the other bidders were developers I think.
Estate agents job is to get the seller and themselves every penny they can. Times are tough for them and many will bend\break rules for their own gains (as many many people do in all other walks of life)
Good Luck!