I actually had a conversation with a local EA last week (I'm in Scotland BTW).. and my question was this:-
"Why do we have the "offers over" situation.....supposing I KNOW what I NEED to purchase my next house... why can't I just put my house on at a fixed price????" ....I was told "oh no, you don't want to do that because that smacks of "desperation" and/or "there's something wrong with the house"

So basically, the EAs encourage the "offers over" situation, but my gut feeling would be that, like in alot of cases in Scotland, you've probably bought before you've sold, so you know what you "need" to achieve to get your next house. The "offers over" is just a way of fuelling the house prices IMHO!! Oooooh not like me to pontificate, but it's something I feel quite strongly about!!

... and I must add that you CAN put it on at a fixed price (after all, it's your house that you're selling), there's no law against it, it's just that the EAs wouldn't advise it!!!