Interesting thread and empathy for your current situation: it will pass and try not to get too overwhelmed.
^
Issues^
I agree with the above, on the optics of downstairs v upstairs: having ample ground floor space amplifies how standard it is upstairs. This is compounded by being the priciest house on the block, the local area and then the house being special.
Spending on dressing could be a false economy, and may not be worth the hassle: I wouldn't and if you do, take advice from someone qualified/experienced before spending.
However, I would want better pictures. In pictures 18/19, removing the duvet entirety and the suitcases would give give a sense of space. Also where are the pictures of the gate, garage and drive, mow the lawn and take a prettier lawn pic. These pics would instantly add extra wow to the house and make it clearer why it's the house on the estate. It probably needs video too. ^^
Price
That said, every house can sell, unless it's overpriced.
a) What comparables did you get from other estate agents and what range did you get?
b) Special houses like this will have an asking price and what you've been told is a floor / selling / price you should accept. I can't see how long yours has been on the market for, but the two need to be rather close, morsel once you've had it on for sale for more than 6 weeks and it's not elicited an acceptable offer (assuming your agent couldn't really price it, so you tested the market).
c) Based on £425k and the^ 155 square meter footage, it's £2,741 a sq m. I don't know the local market, but there is a house - on the estate - that's £3k a sq meter (it's on for £275k and 89 sq m). So your sq m seems comparable, so is the ceiling that's the problem or are you not getting the right buyers to come look?^
Would anyone pay £425k, when a house on the estate is £275? Is the extra £150k worth the garage, the gates, the drive, the extension: and yes I know people who have spent x2 the estate average for that special house.
The real issues are, does your agent know the area, are they getting the right buyers (I say no, and the pics miss the mark and no video (special houses deserve special sales techniques), and will the pricing work for the right buyer, for whom the space works (I assume this would be a young family with a few kids who don't need big bedrooms but lots of communal space). ^^