OP, we had this a lot when we were looking, but it wasn’t is your sale agreed, it was ‘nothing to sell.’ So basically agents all want to know viewers are walking around with upwards of half a million quid in their back pocket - utterly deranged. There was one house we really wanted, but it was an estate sale and the agents claimed the family wanted a chain-free purchase. I told the agents that we mightn’t need to sell our existing property to buy theirs: problem solved from their end. It was both true and untrue insofar as I really didn’t want to do it but if it had come to it and it was that or lose this smashing house I had provisionally agreed to briefly borrow a horrible sum for a short time from a family member until we sold, like a nightmare inducing but interest-free bridging loan.
Had we decided not to go for it I wouldn’t have wasted anyone’s time, as we saw said dream house (aka the moneypit) with a lot of other people at once. No-one even asked who we were on the viewing morning, and we were in and out in ten minutes. Basically, we knew we were buying it before we ever set foot inside.
I can see why people say it’s morally objectionable to lie and viewing could be seen as time wasting if you’re not in a position to buy, say, if the vendors are anxious to sell for any reason and also having to show you round individually. However, speaking as a recent vendor sometimes it does no harm to play the long game. Say they show one lucky would-be purchaser round who’s agreed a sale, they get a deal going, and that deal subsequently falls through? Who’s to say you can’t sell your house quicker or offer more money than someone who ostensibly already has all their ducks in a row (we did) but turns out to be in the collapsing chain from hell. The viewer who hasn’t yet sold theirs just might be the person who’ll buy in the end, which is why when we sold ours we let anyone see it who wanted to, whether their property was on the market or not.
I showed everyone round individually. Truth be told, it was stress-inducing and we had a fair few people I think might have been just in for a nosy, but it wasn’t a shift down the salt-mines. In the end the family I would have wanted to get the house didn’t because the couple who bought it were living with parents so were ready to go - sadly, we needed it done and dusted quickly because of our seller’s demands (which didn’t turn out to be that urgent after all, they just didn’t want messed around). So this might actually be a cautionary tale about why there’s possibly no point torturing yourself if you’re not in a position to proceed 🥲
What if you fall in love with the house and the buyers want you to have it, but it might still have to go to someone who’s in a better position? Won’t that kill you?
If you don’t feel comfortable telling a lie, like ‘it’s for my parents’ which is fair enough, especially if you live locally, why don’t you ask the vendors directly, tell them you love the house, have had your eye on it for a while and would be serious about selling yours for theirs? They can only decline.