Buying and selling sex in a private space in England isn't illegal. But two or more women selling sex in a single property constitutes "brothel-keeping" which is a criminal offence.
Owning a "brothel" is also a criminal offence, which I believe is part of the reason the owner was upset.
He could have used gloves or held the bin with a cloth. And besides, anyone can leave a mess and prostitutes should be fully capable of not leaving a mess.
The article says:
> I found the bin was overflowing with tissues and condoms. And basically what I had to do was pick all that up with my hands.
The sex workers probably have regular testing for STIs, but the clients may not have this testing.