[ig1]

It's very hard to speak generally about tech in finance, you're talking about a sector that employs tens of thousands of developers in London. Some of them are going to be working on boring legacy code and working long hours others are going to be working on cutting edge technology with sensible work-life balance.

Even within different teams at an investment bank you'll likely see huge variations in tech and hours worked.

Speaking more broadly you can find all the things you want in all three different types of company (small / big / finance), it's more about the culture of the specific firm.

Something you might want to consider is becoming a contractor and contracting at a few different places until you find somewhere you'd be comfortable becoming permie.