I chose the Tundra Pure and Dry 5 as my backpacking sleeping bag. It took a fair bit of research and consideration but I settled on the Tundra Pure and Dry 5 down bag to reduce weight and bulk in my pack while considering the ethical implications of using a down bag. 

Tundra make a point of trying to produce their sleeping bags in a way that is as ethical as possible, from workers conditions to the way the ducks/geese are treated and the down harvested for their bags.

This stance on sleeping bag production is what persuaded me to shortlist one of their sleeping bags rather than one made by Rab/Snugpak/Robels/Alpkit etc who seem rather vague (at the time of writing) on production methods. Alpkit made a start on finding where there down came from but it seemed inconclusive.

Apparently Crux also make an effort on the ethical side of their down bags, but their sleeping bags are way out of my price range.

So it seemed clear that either I would have to get a synthetic bag and put up with the extra weight/bulk in comparison to down or get a Tundra down bag.
I got my shortlist down to a few to choose from:
  • Vango Ultralight 400 (2011 version) - Synthetic
  • Snugpak Softie 6 Kestrel - Synthetic
  • Tundra Pure 5 - Down
  • Tundra Pure and Dry 10 - Down

Weight

Both of the sythetic bags came in at over a Kg (around 1.3Kg) compared to the Tundra Pure and Dry 5 which is supposedly around 950g. The other down sleeping bag being a little over a Kg at around 1.1Kg.
 
1-0 down.

Price

Both of the synthetic bags in the shortlist are under £100, the Tundra down bags have an RRP more like £200. At this point I was almost decided that the synthetics lower price make up for their weight/bulk (don't forget the ethical requirement of any down bag to be considered).
 
1-1.

Bulk

I found my local Go Outdoors had both the Tundra bags and the Vango n stock so went to have a look. The down bags win hands down on bulkiness (or lack of), which is a significant factor when the sleeping bag is in your rucksack!
 
Score for down, now in the lead at 2-1.
 

Warmth

This was going to be a bit hit and miss as I had no way to test the bags, so taking into account the manufacturers recommended temperature ranges, opinions on several hiking/camping forums about down vs synthetic and the assumption that you generally get what you pay for I figure the down would probably be the winner here. 
 
While down bags apparently lose a lot of their insulating properties when wet, the last time I recall my bag getting wet was when camping on a boat, never when hiking. So I'm discounting that as a point for consideration. The Tundra Pure and Dry is supposed to have some sort of water resistance but I've not put it to the test.
 
No score either way as I've not tested them to compare!

So, which sleeping bag?

Decision time... down was winning on the scoring shown above, but price was a significant factor in my choice. £200 seems an awful lot to sink on a sleeping bag, so I was still leaning towards the 2011 Vango Ultralite 400. 
 
Then I found the Tundra Pure and Dry 5 on sale at £150 in the Wakefield branch of GoOutdoors, that settled it. Still more than I planned to spend originally but a good price for what should be a very good bag that will last for years (hopefully!).
 

Tundra Pure and Dry 5 performance

I've not yet been camping in the cold with my new bag, but my initial feelings are that it will be a snug night's sleep. I wore it for 10 minutes at home and was quickly starting to sweat, it actually felt cold when I got out of the bag!
 
I've since taken the Pure & Dry 5 bag camping when outside temperatures dropped to just a couple of degrees (C) overnight. I had no problems at all snuggled down in my Tundra down bag, in fact I found I was a little too warm at times! I might even end up getting a lighter/smaller bag for summer use it is that toasty!
 
One thing I couldn't find much information on before buying was the packed size of the Tundra sleeping bags. So I shall add that to this page once I find time to take some photos for comparison.