CDRs are rarely used by the Royal Air Force in the UK.
CDRs often traverse MDAs which may be activated by NOTAM at any time of the day or night and to varying FLs depending on military need. When the MDAs are not being used the CDRs are activated by NOTAM to allow civilian users to plan to fly along them to reduce distance, fuel burn etc.
You can read more about the UK approach in CAP740