Hi, Roisin. I did the same thing: I went in and met with a lawyer, spoke with him about the case, filled out the paperwork to become a client and left without signing after sitting in his conference room for about 10-15 minutes.
I wondered what the heck was wrong with me. I'd left (now) XAH 2 years before, he was abusive, he was lying to me about where he was living and with whom, he lied about having cancer, he was treating our DS like baggage, the list went on and on, but I still couldn't do it.
Dear friends here at SR told me the same thing: So you weren't ready this time. When you're ready, you'll know it and will make it happen. Don't beat yourself up about it, it's a huge decision.
I can tell you they were right. Please know that you can take all the time you need. Remember to be gentle with yourself. Big hugs.