This is what I say if they pull the I'm-not-ready-to-fuck card once I have them at a lay location; I say "Cool. It's settled then. I don't want anything to ever happen between us that we're both not 100% comfortable with. So don't worry, I won't try to go further than you're absolutely ready to go." Then continue on with either a short freeze out, or right back to making out. I get her really turned on...before long, she's practically (or literally) begging for it.
If they say they don't want just a ONS early on (before getting to the lay location), I say "No worries. It's settled then. I don't want anything to happen between us that we're both not 100% comfortable with. So now that sex is off the table, we can settle in and have a fun night." Then I proceed with the rest of the pick up - normally comfort building at that stage.
One time I was with a girl who'd already expressed her concerns about a ONS. We were getting pretty physical on the couch when I felt her tense up and go a little cold. I told her "Look, I know you're unsure about some things. Here's the deal; I'm not going to try to take you back in your bedroom and fuck you unless you specifically ask me to do so. So, no presure. I won't push for more than you're ready for. Now we can relax and enjoy the moment." Then I went right back to kissing her neck, ect. 20 minutes later she says to me, "I want you to take me to my bed."
