Lungs or Legs?

A good friend of mine used to ask me when we were running whether it was my "Lungs or Legs" that were hurting the most...in other words, what is your limiting factor?  At the moment it is lungs because I'm struggling to get my breathing right.  I noticed that I blow air out only on my 2nd and 3rd strokes after each breath, meaning that I still have air to blow out when I go to take another breath...however when I blow air out on all three strokes it causes me to speed up my stroke so that I can get to the next breath quicker. This increases my stroke count and decreases efficiency...I need to get this sorted!

I've had my second swimming lesson which, other than highlighting the above, gave me a fair bit of comfort that I'm moving in the right direction.  I uploaded a video to youtube of my technique:

http://www.youtube.com/watch?v=PSGjxs7ojmk

Check it out and feel free to give me some tips (best to turn the sound off to avoid the background noise).

Race day is approaching, with just 6 weeks to go I'm still only swimming 2 kms per swim and sets of just 300-400m.  I need to step that up in the coming weeks.  

I also trialed a Swimovate watch the other day which gives you information about your swim efficiency etc.  I'm swimming around the 42 mark...30ish is good club level and 20ish is Olympic so I'm on the threshold of becoming a decent swimmer...a lot of work to come though!