I found the delightfully named Qrystal Pharmacy in Borough very easily and they had Ms J's medication ready to go after confirming who I was.

Her flat wasn't far away at all, although I got mildly confused as she had preemptively opened her door when she'd buzzed me in at the ground floor entrance so couldn't quickly locate it as her door was so far open there wasn't a visible number, and as it was on the end of the row I'd initially dismissed it as a cupboard rather than a house.

Mystery quickly solved by deducing it must be that door based on the number of the door next to hers... and she soon had her hands on the treasure. She quickly rifled through the bag to make sure it was all as expected and she expressed just how appreciative she was to have had it dropped off at her door.

Not quite the Crystal Maze but an enjoyable experience nonetheless.