How to access British Second World War Service Files

A BIFHSGO member asked me about accessing her father's Second World War British Army service file at the meeting last Saturday. I could only answer from memory — it's something I haven't done but it turns out I wasn't far off the mark.
The files, still with the Ministry of Defence, are open on application by snail mail for anyone who died 25 or more years ago, and otherwise to next of kin. You need to know the person’s full name, date of birth and (or?) service number in order to fill out the forms, and pay a £30 application fee. It can take several months for an application to be processed.
Official information on who can and how to apply, and the forms, is at
www.gov.uk/get-copy-military-service-records/apply-for-someone-elses-records