Really struggled with W4 R1 but somehow managed it. Went out this morning for day 2 and could not complete the last 5 minute run - had to give up after 3 minutes because my legs were hurting 
Not had this before and I'm going really slowly (the half hour podcast this morning, I managed 3.9km). Feel defeated & not looking forward to the next run.
Should I stick to week 4 for longer, until I can manage it regularly?
Don't feel defeated, look at what you did do, could you have done that a few weeks ago? No! So there you go be proud of your achievement so far.
Without knowing how your legs were hurting it could be that you need to do some stretches, may even be in the wrong type of trainers.
Personally I would take an extra day or two of rest and see how the legs feel and go out for that run again, don't go out feeling like you can't do it, tell yourself you can do, most of the battle is mental.
Well done, be proud and you will get there.
Thank you for your words of encouragement.
It was the bottom of my shins that hurt but they feel fine again now.
Perhaps my body was just telling me I should be in bed at 7am on a Sunday and not out running!
7am that's late 
I have no experience of shin issues so my best advice is still take an extra days rest. The fact they are fine now is great. Your body is adjusting to a whole new set of demands and there will be some niggles.
There's a big jump in the programme week 4. So of course it's going to be harder. I notice you said you struggle to finish R1... But you finished it nonetheless! Well done ! I don't know anything about aches and pains when running, other than mine would hurt sometimes from the build up of lactic acid. So I t's important to not go at it too hard till your body gets used to it and breathe deeply to take in as much oxygen as possible to help break it down. I also would advice you to take an extra rest day. This will give your tired muscles a chance to recover and for you to regroup mentally. I always find a difficult run easier after a 2 day rest. You were so close to doing it last time, I bet you surprise yourself next time. Good luck!
Oh it was your shins... I know even less about shins!! 
good luck anyway !!
Struggled with week 2 run 2...
Week one day one disaster! 
Day 2 of Week 2…Still smiling!
Week 7 day 2 complete 
Couch to 5k Week 2 Day 1
