On the keychain portable charger point I can recommend Tau by Rolling Square (the same company that make the keychain cable you recommend) 
Rolling Square TAU® | Keyring emergency powerbank | Integrated cables | 3 different connections | Magnetic charging dock included |

Morning all, we’re looking forward to seeing everyone later! It looks like it’s 50/50 whether we’ll get rained on but we are keeping calm and carrying on. The plan is to start in Regent’s Park and fall back to Regents Bar and Kitchen for a coffee if the rain does come.

The meeting point is around here: https://maps.app.goo.gl/c71n1uh7MBADQWAb6?g_st=ic

And If it’s raining when you arrive we’ll be in the cafe / bar next door. See you there from 12:30 onwards 🙂