Similar problem owning a a190 and a140, there is the mercedes wis dvd / cds if you can get hold of a copy, covers all mb vehicles. price varies between £100 - £60.
as mentioned on the other 'workshop manual' thread:
try www.autocartec.co.uk they do MB WIS & EPC disks [and other for mitsubushi etc.]
bit difficult to 'communicate with' though, only an internet link no phone or address.. think the WIS [workshop information system]discs[ 2xdvd] are about £70 and the EPC [electronic parts disk] [2xcd]about £50
i dont have the data on the A class but im sure its been used in other mercs so exactly what engine is in there, you know they make new cars with the older engines you know[?]
Having purchased my A160/2002 s/hand, sorry used! twelve months ago. I was most disappointed to find that there was no Haynes or other workshop manual for it, so I decided to put a few bits of information together myself, along with a few pics, adding to it most weeks as and when problems/maintenace became necessery,if you would like to take a look? just link to:- http://homepage.ntlworld.com/albert.rowe be interested to hear your comments as to whether its worth while continuing.