For my new job I'll be arriving at a mainline London station. I'd like to have the flexibility to use either the bus or the tube without having to stop and buy single tickets. To my rail monthly season ticket it seems I can bolt on bus services or tube services, but they are separate products and buying both looks like an expensive way of doing things.
Is there a ticket that I could buy monthly (separately from my rail ticket) that would give me access to both bus and tube services? I have used Travelcards before but am never sure whether they are valid on buses.