I did it! And it was no more difficult than week 1 was actually... meaning yes, it was bloody difficult, but do-able. When I finished w1r3 I mentioned in my blog that I didn't feel that I was ready to move on to week 2, and several people were good enough to take the time and trouble to advise me to at least try it. They were right.
The funny thing was that I didn't even feel like I wanted to do the run, so began to find all sorts of 'omens' that it wouldn't go well this morning. One contact lense fought back and stubbornly refused to go where it was meant to; one of my running shoes concealed itself under my bed so I had to crawl around looking for it; I had forgotten to charge my phone so didn't know if I had enough battery left to keep the lovely Laura going for half an hour... and so on. By this point I had convinced myself that the run would be a disaster... not the best mindset to begin a new week with.
And the stupidest thing, once I actually began to run on the first minute and a half I felt all those anxieties flow away, and I knew I would be able to do it. Sometimes it really is a mental challenge as much as a physical one.
Thanks for the good advice everybody! I'm now on a high for at least the rest of the day, and I wish everyone who is out this weekend a good run too!