OP my first impressions were of student digs and that it was tiny. When I saw the lounge/kitchen/diner pic I thought it was a bedsit.
The storage boxes really are too much and further the impression that the flat is small.
There is too much crammed into the living space.
Removing the computer desk and the grey storage box would go a long way to opening the room up and making it look more spacious.
Hate to say it but having a real sofa rather than daybed and futon would also make a big difference. Try gumtree or local charity furniture shops for a sofa/suite or sofa bed might be an option for short term.
Those storage boxes are really quite oppressive and further the studenty vibe. A chest of drawers or cabinet of some sort would look more inviting and appealing.
The rooms are all a bit bare/plain once you look past the storage issue - just some artwork on the walls and a large rug in the lounge area would brighten it up. Even carrying a theme with the throws and curtains may add a bit more appeal.
A few pots and plants on the balcony would also make it more welcoming.
Floor plan would also be helpful and dressing the bedroom as a double bedroom would again make a big difference - a divan or ottoman storage bed would also help you with the storage issue.
A fold out foam bed would then be ok for your little one to sleep on while you're waiting for sale and could then be folded up during viewings.
Have a ruthless declutter and then bring the estate agents back to retake the photos. Most flats would appeal to singles or young couples. So think about what made the flat appeal when you bought and what would make it appeal to a potential buyer. Also get onto the other agents' websites and nose at the photos of other flats nearby to see how they are dressing their rooms. It may give you some ideas.