The factory workshop manual also known as the Bentley manual. Available from almost any book seller. Amazon, Ebay, Moss, Victoria British
http://www.mossmotors.com/Shop/ViewP...eIndexID=29468
There are also reprints of the shop manual available on CD,
http://www.mossmotors.com/Shop/ViewP...eIndexID=48439
The Moss Motors catalog is also helpful and has some technical articles.