Can you explain broadband speeds to me ?

First heres my comprehending of how it works before the huge broadband speeds came along...a bit is a 0 or a 1, a byte (b) = 8 bits of data , it takes 8 bits of data to make 1 character eg a letter p, kilobit (kb) =1000 bits of data, kilobyte (kb) = 1024 bytes of data, k means 1024, so a 56k modem ( popular around the year 2001) is 1024 x 56= 57344 bits per second (bps) divide 56344 by 8 which is 7168 and thats the maximum number of characters per second your modem can run at. now i want an explination for 8mb and 20mb, is that megabits or megabytes? how many kilobytes in a megabyte and megabite ?? so if i get 8mb broadband from say british telecom whats the maximum download speed i should get in kilobytes eg 8000 and whats the maximum upload speed eg 1600?, then explain what that means in real terms eg its like downloading 20 pages of single sided a4 full or text per second ( i need to comprehend what it will be capable of sending me) and im considering virgin broadband 20mb alsoi need a full explination to all my questions from how ever many people it takes to answer all aspects of what i need to know. a quick 2 line answer isnt what im after. as internet tv is now available i want a fast line hence why i want info on 8mb and 20mb speeds , who ever is most helpful..not nessessarily the quickest to reply will get my points thanks...i agree id love to ask my isp to answer this but i cant stand indian call centers im english
Answer
8mbit (8000kbit) = 1000kbyte (1mbyte) approx. broadband isp like to use bits because it sounds faster yous os measures network.internet speed in bytes be cause its practical.