The apartment was fine, although not what I'd call 'luxury' as advertised. It's a pretty standard room and not somewhere I'd recommend four people staying as it's very small. That said, it was clean, well presented and well located, though it did not look like the pictures (I booked this room as it had a breakfast bar where I was going to work from. There was no breakfast bar).
The biggest issue was the heat. I was on the top floor and it was intolerably hot – 36 degrees at night, even when it was 26 outside. I asked to be moved or to cancel the booking, since it was actually quite dangerous to stay there and impossible to work from during the day, but was instead offered a fan. There's also a boiler in the room which lets off a lot of residual heat. I asked to switch this off but no one replied. I ended up having to pay for a co-working space, so the cost was amplified. As such, I would not recommend staying here in the summer and I would implore the owners to invest in AC. Luxury accommodation would have it as standard.