I started my search on the GTTR website, finding all the unis in my desired location (London) offering Secondary English. From there, I tried contacting students and read through Ofsted reports and looked at general rankings, but mainly to see what was being said about the unis. I didn't base my decision solely on ratings, not even close. It may have factored in at about 15%, but that's it. I also visited some of them to get a feel for the area. I considered Oxford and Cambridge as well, but it wasn't an ideal situation for me.
My personal situation it was ultimately affected my decision. I had to consider my partner, our financial situation, and the fact that I'm non-EU and will be about 6 months shy of qualifying for home fees. I also knew that I planned on completing a Masters, so I looked to make sure the uni offered MA credit and looked through their MA options, as I'd prefer to stay at the same uni (assuming all goes well) for my MA. In the end, I chose KCL, and I got in, followed by IoE, UEL and London Met.
As for any rankings/ratings. When I decided to put KCL first, their Ofsted wasn't fantastic with a Grade 2 (pretty much across the board), but it also turns out that they have really made some changes and now have a Grade 1 across the board.