I used bleach one cupfull for 40 gallons, run the taps to kill the bacteria in the hoses, empty the tank and put the bleach in then fill, leave for 12 hours, flush twice running the taps to empty the tank then fill.
I'd completely forgotten that I'd even posted in this thread when it first started. I don't even remember typing my previous posts but reading them now has answered some of my own questions.