Our experience with Singular Stays was a nightmare.
I was sent a contract on the morning of check-in informing me that we needed to pay a €400 deposit. This amount should have been £175.56, which I had proof of in my confirmation from Airbnb. When I looked into the contract further, it also showed we'd be liable to pay utility costs. While contracts are allowed, these terms were not stated in the listing, as Airbnb confirmed the host had broken their rules and we were refunded, leaving us scrambling to find alternative accommodation at 8pm.
Singular Stays were unresponsive before, during and after the time of check-in, leaving us in the dark. The only time they'd answer would be to push me to sign and pay the €400, ignoring any other questions. Sending the contract on the day also felt like a way to pressure you into signing. All I can say is that you should avoid this and any other of their listings (they have many). I wish I had seen their host/online reviews before booking.