30 mins of action wasn't mentioned coz you didnt ask the question

Its not rocket science - pose like "i'm xx mins late (sorry - again) are you still ok for the hour or do you wanna shorten the booking ?"
See what the answer is & wedge her up a bit more for being late etc
I hope you didnt rock up with £5 notes, imagine how long that would take to count out ... only 600
A budget of 600 for an hour brings up soooo many options in London & you pick this one ?
What was the primary motivator ?