I can't tell how old it is, or what the state of repair is - I'd want to pull out all the drawers and see.
To me - and I'm no expert, just someone who likes 'old brown furniture' - it looks as if it could easily be pre-twentieth-century. So I would expect the price to be over £500. If it's older, and in really good nick, I've seen them go for more like £2000. If they're very old - and I don't think this is, but as I say, I don't know - they can go into the tens of thousands.
I think with anything like this, you have to just buy what you like. It it is worth £400 to you, then buy it! I have a huge dining table which I adore. It is nothing very special - it's a Waring and Gillow product, hundreds like it, but it is very solid, beautifully made, and I was delighted to spend £420 on it, because my second-favourite option for the space was a much smaller Habitat table, which I think I would always have regretted. As it stands, I have a lovely table that extends to seat 20 people; it has a beautiful easy extension mechanism you can work with one hand, and the patina is gorgeous.
I nearly fell off my chair when I looked at the prices of modern tables made out of solid wood! Never in my life could I justify one of them! And the ones I saw were mostly cheaper-looking at less sturdy.
OTOH, if you feel ripped off, then don't bother! Antiques rarely keep much resale value, unless they are flawless and very unusual, and you'd be too nervous to use them if they did. Better to compare it to the price of a new piece of furniture, and think whether that makes you feel good or bad about it.