the EA would normally let anyone interested in the house know the house is gone and not arrange any viewings ...
also, why would vendors allow it if they are interested in the sale?
Sale agreed doesn't really mean anything until contacts are signed as the house can still be viewed and a higher bidder can take your place. But in general the auctioneer will not arrange any more viewings and will tell prospective clients that the house is sale agreed. In this market it's not something to worry about.