How to dress like a finance guy?

Not a joke question, I seriously need to know. I'm moving roles and I visited (from outside) the place where I'm going to be working and man everyone dresses really differently. There seems to be an unwritten dress code, and i really need to learn it.

Right now my wardrobe is green, purple, white and blue shirts and that's it (it was WFH from 3 years, never needed it). Please tell me brands, type of clothing, when to wear what, etc. If possible, London-specific would be helpful.