If you are stopping in Twizel for a few days and need a place to stay I would recommend the Mackenzie Country Inn. It's warm, the staff are friendly and happy to help, the food is good and it's a perfect location to base your trip from. Click on the link below for more information.
Located a few minutes outside of Twizel near the base of Mt Cook is the Hermitage Hotel. This hotel offers quality accommodation in a truly spectacular alpine environment that you will never forget. Click on the link below for more information
If you are after a budget accommodation option then the Ruataniwha Holiday Park. The Ruataniwha Holiday Park offers all the basic amenities that you will need. Click on the link below for more information.