Tomorrow I am travelling from Hampshire to Rochester and will be
breaking my journey for several hours in London.

My ticket is a "via London" one and will allow me to travel on the
Tube from Waterloo to Kings Cross St Pancras should I decide to travel
on the new high speed line, from where I live I appear to be able to
use this route on a standard ticket and indeed I have done so in the
past.

However as I am breaking my journey my initial Tube journey will
probably be to Baker Street.

Will my ticket allow me to do this? I could probably go to Marylebone
instead if it would help to go to a station with a National Rail
connection. I obviously expect to have to use my PAYG Oyster for any
subsequent tube journeys - but can I at least get one out of it?

Tx.