Sounds like the archetypal "entitled" guest that all hosts wish to avoid @Louise543 !
- Try & put it behind you, & be grateful you dodged that bullet! - Goodness knows what else they'd have found fault with, had they actually stayed!
- IF I were to reply, I might consider explaining that the "cleaning fee" is actually a way of rewarding guests who stay longer, & getting weekenders to pay proportionately more, rather than adding that £80 to the nightly rate, which would not be to the guests' advantage, cos a higher nightly rate would result in more commission to Airbnb. - Just a thought.
- Or just let them know that if the cleaning fee were removed, the nightly rate would need to be increased.....
Of course you don't HAVE to justify yourself, & I think @Emilia42 's response is great! (I sometimes like to give a little education to folks with unreasonable attitudes & demands! - Re what Airbnb is & is not! Reciprocal/Respect are words which spring to mind....)
Personally I don't charge a cleaning fee BECAUSE I don't want certain elements to view it as a rip off, or a deceitful hidden charge, tho' I'm wondering about introducing the minimum £4 to compensate for the 1-nighters, knowing it would make hardly any difference to the 4-nighters.....