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The unknown sourced down is a reasoable concern.
The temp rating being lower isn't so important as i was thinking of still using a sleeping bag but wanted something easily packable and cheap to use as an underquilt in addition.
Another idea just buy a bit of tyvek and add loops to it so I can hang it on the underside to block windchill
laner-
http://theultimatehang.com/2013/01/22/diy-poncho-liner-under-quilt-pluq-sew-and-no-sew/
Think I'd go for something like this as a 'dipping my toe' solution, poncho liners are £20-25 on eBay. You could probably even just get away with attaching some shock cord directly to the ties for a super easy bodge version. Obviously heavier than down but at least you know you're getting reliable insulation, it's waterproof, and your conscience can remain clear.
Whatever you do I'd be interested to know the results.
ThePeginator
I personally wouldn't even entertain the idea of buying a down product that wasn't from a reputable brand.. and even then to a degree, but it's each to their own.
The other thing worth noting is that with only 150g of 650fp down, I'd take the temp ratings with a LARGE pinch of salt. A Rab Neutrino 200 is a full bag with 200g of 800fp filling and it's ratings are only 1-2 degrees better than the nature hike. I'm sure the nature hike would be better than nothing but not even close to what they claim.