Hi Josefina,
Not sure if I can help you with fintech specific events; I work for a fintech myself but I end up going to mainly marketing and entrepreneuship events. I recommend you keep an eye on techlondon.io slack channel and on eventhunt.io/. If you are Portuguese, we also have some Portuguese meet ups with other startupers, if you are not, feel free to join in any case 
Hope this helps!
Andreia
