Pratical question Torres del Paine, Chile

Hi Everyone,
I'm preparing a 3-week trip in Chile with my brother beginning of December. In Torres del Paine it doesn't look like there is any middle solution between very expensive hotels and camping (don't have a warm enough sleeping bag for that solution).

So, my first question is : do you know of any affordable accomodation to sleep inside, in the park or closer than Puerto Natales. ?
Second question is : we don't want to do the "w" circuit (too long) but we are considering a one-day out and one-day coming back, sleeping in a refugion. But we can't hike carrying all our luggage! We won't have a car to lock thing in, so does anyone can tell me if there are lockers somewhere inside the park, so we can only take what we need for the hike? Thank you very much for your help!

Françoise