Looking to find great midsized companies in London

I like my current job but I'd like to see what else there could be. I'm not set on leaving so I don't want to get a recruiter or anything. Just wanna test the waters.

I've been at my job for nearly 3 years and it started as a grad scheme - it has since not been as good as it used to due to cultural and managerial decisions.

Im full stack react, node.js but Id like more of a back end role next time.

I want to look at some companies​ but I've never thought about it before so I don't know any good tech companies to look at. I want the whole start up vibe with a crazy tech office etc and some cool work.

Anyone know where I can find a list of companies like this without getting a recruiter involved?