Gosh OP, I am looking at the photos again and so angry on your behalf. The agents have done an absolutely dreadful job of taking the photos.
When you do re-take them, my thoughts on each photo below:
Photo 1: fine; this flat could benefit from more photos of the surrounding area to bring out the amenities you mentioned on this thread
Photo 2: the photo you took of this same room is much better and I like the pink as it appears in that photo as it warms up the room; I don't think stark white would work as well given it is a fairly dark space and white can often just highlight that. Would suggest perhaps changing the location of the green chair to have it next to the window (below the wolf poster) angled towards the sofa. The two wooden shelving / storage units look a bit odd next to one another - anything you could about those?
Photo 3: absolutely dreadful photo! The right photographer should get the angle and lighting right so it doesn't look so dark in the dining area, move the kids' chairs to either side so they are not the focus of the photo, maybe try a bigger mirror on the back wall if you have one or can borrow / buy one (the TK Maxx in the Charlton retail park always has great inexpensive mirrors)
Photo 4: The kitchen could do with a bit more of a dressing up. Maybe a cheery picture next to extractor fan, wooden cheese/chopping board or similar to warm up the cold white and grey. If possible, take the photo with the lights turned off - the glare from the spotlights is quite distracting.
Photo 5: see points for photos 3 and 4 above. I now notice the console in the dining area more so may be an idea to carry through a colour from the kitchen to console top to warm up both of them a bit more. Ooh, maybe some potted plants and a fruit bowl in the kitchen and flower vase on the console in coordinating colours. Angles and lighting are bad again.
Photo 6: While I like the pink in the living room, I am not keen on the pink in the bedroom. If you can, could you paint it something dark and make it cosy and cocooning? www.pinterest.com/pin/458874649542101649/
Are you able to put some window dressing on the window -- even just a curtain rod and solid curtains from Ikea or similar? Could you swap the bedside tables for something with hidden storage. Suggest tucking away all the cables and wires and also putting on white bedding and then maybe a cosy throw and cushions.
Photo 7: Are you able to either get doors for the open wardrobe, or, if that is too expensive (which it may well be), just a long curtain rod and plain curtains? The sheepskin looks too small for its spot - try a larger area rug if you would like to have one (the sheepskin could go to the foot of the bed)
Photo 8: room looks good. Lighting in the photo looks bad.
Photo 9: Can you get window dressing for this window as well, just to make it clearer it is a window?
Photo 10: bad angle. Swap towel for white towels, get the washing basket out of the photo, remove the other visual clutter (blue car on the left?). If you can, maybe change the light fittings. Unfortunately, the bathroom looks quite dated but that's for the next owner to deal with if they want to.
Photo 11: another terrible angle. Points above still stand. Use a white bathmat too.
Photo 12: See previous points for dining space plus remove the dog bowls and printer (?) from the shot
Photo 13: this room looks out of sync with the rest of the flat. The lamp on the piano looks, the light fittings are weirdly spaced and I kept thinking it was a tiny lounge with low ceilings but couldn't figure out how it connected to the rest of the living space. Can the piano move to a different spot? If so, may make sense to then centre the sofa between the lights and style it as a bedroom. Could the piano go to the spot in the living / dining room currently occupied by the larger wooden unit?
Photo 14: tuck away the wires and chargers and maybe try to get a wider angle photo of this room
Photos 15 and 16: ufff, what was the estate agent thinking?! Get rid of photo 15 altogether. Clear our all the clutter (the bag of toys, the shampoo bottles, the things hanging behind the door reflected in the shower enclosure, the step ladder), replace the black open storage in the back with covered storage in white or a cream/beige colour (google "slim bathroom storage", lots of options came up) and take the photo form right in the doorway or just outside so you can get the full height. Put a fun picture next to the mirror to draw attention away from the fittings a bit.
More pictures: of the development and of the living room from above showing the full height
In some ways, this flat is similar to what you are selling -- a flat where the development is almost as much of, if not more of, a selling point as the flat itself and it does some things really well (although, of course, it has also not sold yet so there's that market and price point thing again): www.themodernhouse.com/sales-list/the-helios/