MARTIN/GRAY/TRAVELL London area

[Jjaazzyy]

I am just getting started on my family history. What I have so far is all from memory. My family is from the London area. Croydon - Thorton Heath area for Gray, and central to North London for Martin and Travell. I do know that the Martin/Travell side of the family were hansom(spelling?) drivers (today they would be taxi-cab drivers). Any help/information or pointers on how to search and what to look for would be appreciated. Thanks