Not sure how useful a map is for Borstal Prison (now HMP Rochester) as the authorities are not keen on people mooching about outside it. Further down Fort Road you will find Borstal Fort. Which was part of a defensive line of forts to protect Chatham Dockyard. It has seen better days.
If you are interested and want to read more about Borstals then why not try some of these works:
Some rather fabulous pictures from the University of Warwick
Some interesting quotes and notes from the National Archives Learning Curve
A great website which looks at different children's homes in this case Borstal
Website called Inside Gate which explains life behind bars at Borstal
A little slice of movie trivia on the film and tv programme Scum
Borstal. A Critical Survey written by W. A. Elkin, D. B. Kittermaster published by the Howard League for Penal Reform published in 1951.
Page on parliament and penal reform with links to various Prevention of Crime Acts
Report on how 12 boys made a human pyramid to escape from the Borstal they were housed in
The British Borstal Training System by John Warder and Reg Wilson from the The Journal of Criminal Law and Criminology (1973)
Borstal Success and the Quality of Borstal Inmates by Alan Little from the British Journal of Criminology (1962)
Oxford Dictionary of National Biography on Alexander Paterson
Website on Alexander Paterson's reforms