In reply to Sam C:
Yes Puerto Natales has various small supermarkets, outdoor shops and places to stock up on food. Although I'd take food with you are as choice is limited and it's more expensive than in centres of population. We were comfortably under-weigh on the plane from Santiago with 12 days of food in our packs.
A Czech trekker burnt down a large area of pristine woodland a few years ago creating a huge fire with a camping stove so that is presumably why regulations have become stricter.
Not sure what the link to Doite is for. They are a Chilean outdoor brand that makes poor quality, cheap gear, leaky tents etc (although I have a Doite hat I'm rather fond of). They don't tend to have their own shops although there is one in Santiago.