I completed this yesterday on what was a new route for me.
I found a long cycle path near where I live that is perfect for these runs. When I go again though I will park my car nearer to the start of the path as negotiating a couple of small lanes on foot crammed with parked and queueing traffic waiting to get into the boot sale at the adjacent school wasn't much fun.
The run itself was pretty straight forward and as the route was new and I had no visual judge of distance I had the "Distance 2k" message in my ear from my Nike+ Running app before I knew it and needed to turn around.
by the time I was into the second 5 minute run I was blowing quite hard again, but realised had let my breathing technique slip. Once I remembered Laura's advice I was able to get it mostly under control, although by then it was much more difficult to respond to the multitude of "good mornings" from other users of the path.
I finished the programme well before I was able to get back to my car and managed to get in another slow run of about 2-3 minutes before I started to warm down as I knew the car was nearby.
All in all I felt good after finishing and I'be begun to notice that my recovery time is also improving as each week goes by.
There's rain forecast for the next few days in my area (South Wales) so I may have to wait a couple of days to finish W4, but I now also find I get itchy for a run when I haven't been able to get out on a day when I normally would have, so that has to be a good sign!