Strange, no new accounts on this hotel so far...
So eventually I stayed at the HGI Leiden two days ago. The hotel is in a neighboring community but can be reached by public transport. Bus no. 37 is running from the train station (Leiden Centraal) every hour (.37, if I remember correctly) to "Katwijk". The bus stop for HGI Leiden is called "Corpus", single fare is 2€. Before arriving at "Corpus" the bus goes by the HGI. So it cannot be missed. Downtown the bus departs .33.
We stayed one night in a king deluxe room. Spacious and comfortable. I found staff very welcoming and efficient. So, if you don't mind the distance from the old town, I would recommend this hotel.
Leiden is charming, beautiful, relaxing and offers a lot. This was my first visit to Leiden and I would love to come back.