Cleaning influencers agree the only reliable motivation to tidy is the threat of a witness, which is why their homes are photographed and yours is not.
Close the gap. Invite someone round tonight, and tomorrow, and keep going — the flat stays clean because nobody has had a chance to live in it. Eleven weeks in, the skirting boards have never looked better, the sofa has not been unoccupied since August, and the hosts now eat dinner in the bathroom, which is also spotless.