I'm not in the UK, but it often makes me smile to hear all the tips. Paint this, move that, change the duvet cover. That flat looks very good to me, and most of the works are just cosmetic, easily done by the buyer if they want it badly enough.
Where I am ROI, most try and make their properties look ok, but don't go for showhome condition either. Very few here would change a kitchen or bathroom, that's for the buyer to do if they want the house, and sales are moving here too.
When our mum passed away we had to sell her house. It had been rented for 12 years, but it was regularly maintained, ie we had gutters cleaned, garden kept nice, painted regularly. The kitchen was old like myself. It sold, honestly within three weeks, but although it needed a bit of updating, it was the location that did it, and we got the Molly Maids and Men in to clean it within an inch of its life when the last tenant left.
Sorry for going on, but it is rare for flats to have ANY outside space. This flat has a balcony. That is a great feature, as is the location.
Might be price and nervousness re Covid. Best of luck OP.