We had 3 wonderful nights in the Surf Hostel.
It is really beautiful, comfortable and the hosts are friendly and helpful. The room and the bathroom were clean and cosy. Even though the place is a Hostel you really have time for yourself if you want to.
But when you see the other guests and the hosts at breakfast ( oh man that breakfast was good..... made standing up way easier;)) you can be sure to have nice and insteresting chats.
The hostel is not far away from the beach and the city centre even though it is a little walk.
I would recommend this hostel to everyone and have now one more reason to come back to Biarritz (The town itself is also pretty stunning)