Oh God, I met up with that guy too! I'm very new to this business and only created a profile on AW recently (I didn't even know about the site a couple of weeks ago!), and was going through ads on CL... I didn't think ?50 was much - even if I was new I realised that it must be below the going rate - but I was about to go for drinks with friends near where he lived and thought I'd pop in to see him and have an exciting quickie before heading for a night out.
Everything went fairly well in the beginning - despite the fact he looked quite a bit older than in his blurry photo - and he wanted me to lie down and go down on me. Then he got on top of me and I could tell he wanted to start fucking me, and I suggested we get a condom... which totally killed the mood for him!!! UNBELIEVABLE. He was hoping to trick a naive newbie girl into have bareback sex for almost no money, basically. That's probably why he made you leave when you asked for money upfront - he realised you had a professional attitude and would not let him sleep with you bareback.
What happened after that was that he just got up and said 'It's not going to work' and became quite angry. I put my clothes on started to leave - I hadn't asked for the money at any point and was expecting him not to pay me but I didn't really care as I just wanted to get out... but when I got my coat I noticed he'd left sixty pounds next to it, which I then spent on a great night out which ended in non-paid sex with a handsome stranger. Happy ending at least