Until 1991 the guidance for flats was CP3 chapter 4 part 1- editions were published in 1948, 1963 and 1971. The Building Regulations between 1984 and 1991 were covered by a document called "Mandatory Rules for Means of Escape", as between 1984 and 1991 the fire authority was responsible for the enforcement of Building Regulation functional reguirement B1- Means of escape from fire. In 1991 the Bickerdyke Allen report transferred responsibility to the Building Authority.
I have some of the documents electronically, but if you take a look at the following link you can download a draft copy of Colin Todds latest tome which is an excellent and complete compendium of everything you need to know about the design of flats.
You may have to register with the LGA website first.
http://www.lga.gov.uk/lga/tio/18055650