Never met Estelle, but I am really sorry to read those news.
I feel a bit off following those sad news by telling my experience with Sylvie/Nicole - I hope you don't mind and apologies in advance. I am trying to contribute to the conversation.
I met Sylvie twice a couple of years ago, when she was still at Allure. She was based in Vauxhall and charged £300 (very soon though her prices were up and before leaving Allure she had a minimum of two hours for meeting -never met her with those prices).
My two times with her were spectacular -for me. Just to warn you, I don't have too much experience punting, so more seasoned members may have a different experience, but we kind of 'clicked' in bed and some of the best sex of my life was with her. I liked her a lot physically, tall (around 5 10 I guess), with long limbs, but I warn you, a big tattoo in her back (in case you don't like that - I don't mind).
I remember services were DFK, OWO, A-Levels (initiated by her with a sensual 'they told me you want to fuck me in the ass'), CIF received with a smile, CIM, rimming on me. In between rounds you could have a really good chat, and she has a really witty sense of humour -she can make you laugh while you recover.
I never met her in a duo, but there are positive reports here. These experiences are a few years old, but I recently read a positive report now that she is at Blue Monday.
Having said all that, my humble impression is that she doesn't reach the heights of a filthy PSE (based on reports of more experienced members). No gagging, no ws, and she seems to be more dom than sub. I haven't met Camille, but my impression is that both offer a similar level of services.
I would definitely meet Sylvie again if she was charging £300 or £350, but I personally would not pay £600 to meet her -having said that, I am aware that we all value money differently.