NYE fireworks in London

Soooo, I had my heart set on fireworks while we're in London on NYE. Luckily, I went online to do a little research and found that you have to buy tickets (to go to keep the numbers reduced) and there were still tickets available for the North 2 area (between Temple and Embankment). I'm curious, and cannot find it online, whether there will be rules about what you can bring inside the "venue". I mean, size of bags and items that you can take in. My husband has this tiny golf tripod seat and it's small enough to easily stick in my baggage. But I don't want to bother if you can't bring anything like that with you. It would be nice to have a way to rest my bad knees since we'll be out there for upwards of five hours. And then I wondered if there were portable toilets in the area. Considering how early you need to be there, I'm sure I'll have to go at some point! I'm pretty excited, and I wanted an idea of what to expect so there aren't any surprises upon arrival. The advice I have found online advises you to wait until about 1am (when the music ends) to venture to the Tube when the crowds have thinned a bit. If you have horror stories to tell, please refrain. The tickets are purchased, so we're going! I read a blog from someone who went last year and wished I hadn't. There were stories of violence against strangers and the like. I'm hoping that the new system will reduce crowds so it's more controlled!