Don’t be pressured by the EA.
This does seem a v low price for a 3 bed house in Clapham. And I am suspicious that a vendor would consider any offer from a buyer who is not under offer. Or that an EA would encourage it. Dexter’s are the new Foxtons for pushiness: I bet the contract period with the vendor is running out and they want to magic up an offer
This could work in your favour IF you really want the house and they accept your offer. The house is great, the general location is great, the specifics of the location are the compromise for the price.
I don’t see that it would be especially hard to sell on the same premise in the future.
So if you want it irrespective of EA pressure, make your offer.
(but beware : if you take much longer to sell you may well get gazumped. Will they take it off the market if offer is accepted? Do Dr gets take a deposit on offer accepted? I bet they do. The minute you are under offer insist they take it off the market)
If you are not sure, keep looking.
You have presumably looked at what’s on offer in Balham for your budget?