I am fairly new to the area and whole 11+ but am completing my online admission choices and am putting Dr Challoner's High School as 1st choice then Chesham High as 2nd.
I live in Chesham (opposite Chesham Park) but am just a bit concerned as I spoke to someone at the council today who said that it is possible that even if daughter passes 11+ we could get neither - is this likely?
Whoever you spoke to at the council has misinformed you.
You live barely a mile from CHS, and they have routinely offered places to many children out of county for years gone by so, living a stone's throw away, you will be assured of a place. If not, I will eat my hat - not an appetising prospect!
The same almost certainly applies for DCHGS, who have been able to offer places to all catchment applicants for the last 2 years, and you are in catchment. You are more distant from the school, so there can be no guarantees that the allocation distance won't change, although I doubt there will be a radical shift in the next year.
Your choices look very sound on all past experience - DCHGS then CHS.