If there's still time, I'd really recomment getting your family to get you a Nalgene bottle instead, or even just use a standard mineral water bottle. Sigg bottles suffer the fatal flaw that extremely cold metal is not something you want against your lips.

Thermos flasks on the other hand are pretty awesome. Cup of tea at the top of a shag = super awesome.

Wow, they must be good if they're super awesome!

Ok, thanks Luke. What is a nalgene bottle?

They're plastic bottles with wide lids, about the same size as a sigg. More or less equally bomb proof but easily filled from streams and not metal

However not entirely bomb proof - Luke managed to drop one a couple of hundred meters down a scree slope from a shag earlier this year and having since checked it's water tightness there is a small chip near the mouth which makes it not quite water tight when I tested it with a new lid (the original lid of less indestructable material sadly did not fully survive it's adventure).

I recommend Robinsons 1L squash bottles (after you've drank the squash silly) as fantastic water bottles - thicker and more durable than a standard plastic bottle, much cheaper and with free squash!