So, I was apprehensive about starting Week 5 today, but also looking forward to just getting on and trying it, but then managed to fall out of the front door last night and twist my ankle 
How long should I leave it before I start running again and should I go back to a previous level if I have to leave it for a few days?
There is no definitive answer, but speaking from experience, it will take longer than you want it to if you try too soon. Keep it strapped-up, rest it when you can and try gentle walking. If it hurts, STOP.
It is much better to rest it for a couple of weeks than aggrivate it and be off it for a couple of months.
Look after it, and you will be back in time for the summer!!
Where to start again?
When to start again
Sprained ankle: when is it safe to run again?
Where to start again?? :-( 
Where to start again? 
