I have been following this thread with great interest and envy because my experience has been frustratingly different.
I work mainly within the London postal code areas. When I included costs for travel time and fare in my terms and conditions
I was openly challenged by prospective clients. And when I included them in my professional fees , I was told I was too expensive and they preferred to go with another SLT who reportedly had quoted less !
Having thought hard about a viable solution, I have re-assessed my professional fees and I don’t charge travel time or fare for London postal code areas and I tell prosective clients so. It seems to work but perhaps not ideal!