I stay here often, as other than the youth hostel, it's one of the few super budget options under 35 euro per night in the centre of Calais I feel safe in.
I've stayed in possibly half the rooms and they do vary in quality from ok to not really ok. The mattresses are fine. The towels and bedding are clean. The rooms are clean. It's the fixtures such as showers, toilets, heating that are variable. I'm there just to sleep, so I am happy with the price which varies between 25 and 35 euro per night.
The employees make up for the shortcomings in this hotel, they are indeed very helpful and kind.
Linked hotel is Citadel, rooms a bit better there, but it's noisier there, you need to collect the key from the Belazur.
This sort of hotel won't suit everyone, just people who care about having a comfortable bed and a shower.