Hello
Have you had a look at the admissions policy for CCHS on the school's website?
http://www.cchs.co.uk/wp-content/uploads/2018/02/Admissions-Policy-for-2019-Entry.pdf Permanent Home Address
Only one address can be used for the application. In applying these admission arrangements ‘permanent home address’ will be defined as the permanent place of residence of the parent with whom the pupil spends the majority of the school week (Sunday to Thursday nights inclusive) at the time the online registration form is submitted for the CCHS Entrance Test, or the date it is received by the Admissions Office, if applying by post. The exception to this is if the family are returning from abroad to a previous permanent place of residence within the priority area (documentary evidence will be required), are members of the Diplomatic Service or Armed Forces. So as things stood for those who took the exam last September, the last date by which the candidate had to be living within catchment for at least the majority of the school week was June 27th 2018, the date registration closed.
And no, there are no named feeder schools.
Bear in mind that there is no guarantee that a candidate will actually qualify for a place, so you might think to look at the other secondary schools within the catchment area, taking their admissions criteria carefully into consideration. You can check the priority admissions area for addresses in Essex on the Essex CC website, as well as each school's policy in the Secondsry Admissions booklet, which is also on the website,
As for keeping your DD at her Redbridge school until the end of year 6, it does solve the problem for you of finding a mid-year place at a primary school near your new address, so that's up to you. However, if you decide to move to somewhere within the CCHS catchment area where the non-selective alternative does have 'attending a specified feeder school' as a higher criterion than 'living in priority admissions area', you might want to consider applying for a local place.