The stay was fine once I was in. There was a problem on arrival, though, as I'd been informed that someone called Connor works as the porter until 7pm and that Mohammed is the security guard who could let me in if I arrived after that time. Unfortunately, when I arrived, the security guard was a different one and said he hadn't been briefed to give me any keys. I think that Reception may have been told I was coming, but this security guard was very wary about granting me access and he told me Connor was on holiday and Mohammed no longer worked there.
Kian, the host, was very quick to reply to me at 11pm when I let him know what had happened and he emailed and spoke with the security guard. I got in about half an hour later, but it wasn't an ideal start. In future, I'm confident Kian will be more informed about who's working there and will make sure they're able to let guests in, because it's not good when you need to get up early the next day and you spend some time wondering if you're going to get access.
All that said, Kian was very responsive and apologetic and the situation was resolved. What's more, everything was fine with the apartment and the rest of the stay.