My go to Thai girl these days is Apple Pie on adultwork, based in Kings Cross 2 mins from the station. She's not in Zizzi's league, but then who is these days? The Thai scene in London isn't what it was 5 years ago. You could also try Emma in Lancaster gate, she's on all the main Thai agency sites. Seen her twice, great time both times, and she even let me film once she covered her face on one occasion. A little bit scatty at times, she reminds me a bit of Maria of old.