I turned up to my pre-paid appointment EIGHT minutes late because I couldn't find the place (I'm new to London) and even called in advance to let them know this! When I got there they were closing up a few minutes early - I said "but I just spoke to you, I have an appointment" and the girl just sneered at me and said "15 minutes ago you did". No apology or offer of a refund or even a rebook - guess they've got my money now so they don't care!
I'm extremely disappointed and won't ever be going back.