So, I have now done the first run of W5 - and it wasn't as bad as I expected. In fact, the 3 x 5 mins was one minute less than I ran in W4. But I found this run harder going than the last one.
I was tired as I'd been up to Suffolk and back to see my Mum. I had also had a couple of (small) glasses of wine at lunch - tut tut - but I had drunk 1.5 pints of water to rehydrate before setting out.
I also picked a busy time to run along the canal towpath, as there were loads of cyclists obviously coming back from work. This meant that my runs were a bit chaotic - a case of "speed up - stop - normal pace - really slow - flatten myself against wall to let someone go by".
But I did it! And, as I was about 15 minutes away from home when the session ended, I did a couple of mini-jogs to get me home faster. Running feels much more relaxed when you are doing it just as a way to get you somewhere, rather than as a specific goal.