I met a vendor recently who had five EAs in, and although he wasn't selling for as much as you, the range they gave him was similarly disturbing.
Eventually, he settled on a range that was closest to what three told him, averaged out.
The SE12 market:
If I put a price range of 400-550k for SE12 in Rightmove, also click the 'sold' button, it brings up 65 properties (with no other criteria, they could be caravans for all I know). Of those, from my Chrome add-on, I can see that 21/65 of those properties have reduced their asking prices.
I've been seeing quite a lot of really overpriced houses this year, albeit not in London, so either EAs are vastly overpricing them or homeowners are so desperate to get top money for their house because of the unexpectedly higher mortgage rates; possibly a combination of the both. I've definitely read articles from a few months ago saying homeowners are instructing EAs to put houses on for too much money (difficult to know who believe, it could've been an EA writing that!).
You can certainly look on the Land Registry for houses that have sold in the last year, look those houses up to see how similar they are to yours, pull up the Zoopla advert for the house, and look to see what Zoopla thinks that sold house is currently worth. It's a lot of work and it's not guaranteed to be accurate; Zoopla is notorious for not being accurate, but if there are enough of them and they are all showing a similar-ish current value, maybe that will help. Personally, what I would do is:
- Call 425 and 525 EA and say 'I really like your firm but before I appoint you, can you tell me why you have valued my home at £100k more/less than another agent who visited?' and see if you can get the truth out of them. Probably what you'll find is:
a) 425k will give you a quick, immediate sale, from an agent who's very familiar with the market and wants their commission quickly
b) 525k is them telling you what they think you will want to hear; in a month or two's time, they'll call you, blame the slowness of the market and suggest 'maybe we should reduce it by 25k to see if that gets more people through the door?'
That's a known strategy so they have lots of houses on their books, they don't really care if they don't sell at that price point; as long as they have lots on their books, more people will come to them, and the commission evens out across numbers, instead of the amounts the homes sold from. I would also
c) Get a 4th and 5th agent in. Much easier to get a reasonable average when you have five numbers to work with.
d) The Chrome add-on that tells me how much houses have been reduced to and by how much is called Property Log. It's free for 1 month.
Also, I used to live right next to Lee train station. Hi hi!
Good luck.