My biggest regret was with "That one" that I'm not allowed to mention anymore. When I started seeing her she was offering sex as well as fetish services but I booked her only for fetish stuff. By the time I wanted sex with her too, she stopped offering it.
So of all the escorts I have booked and had sex with, she isn't one of them.
Fortunately I did get my way with a few of my desires at least once. In most cases it was simply because they were not London based.
victoria_lovelove who used to be on UKE is one who got away, disappeared when the site went down, but now we have the very gorgeous "Sonnya Petite" there. She is the one highest on my hotlist that I haven't yet been with.