The venue is a very short stroll from Liverpool St station. If you're really worried there's a bus stop right outside the venue.

There's a police station that's visible for the entirety of the walk between the station and the bar. Perhaps you can ask one of the officers to hold your hand if your mum is unavailable on the night?

Dodgy how? There's always loads of people there every night of the week: it's very safe.

Dodgy? It's the best part of London :)