I have a couple of questions on battery care if anyone can answer them for me?
Do I switch battery off when putting it on charge?
No check with battery supplier but normally it needs to be on so that the BMS (battery management system) can do it job (balancing the power between the numerous cells.
Do I use battery until totally flat before recharging (someone once told me rechargeable batteries needed to be empty now and again to get a proper full charge into them, maybe talking phone batteries at time)?
No the received wisdom seems to be, Charge it & use it - but you can improve upon that by not letting it go below 20%, if unused for a month leave it around 60% & check monthly & fully charge just before it gets to 20% & then use to take it back down to 60%. The reason to fully charge is that most BMS only balance from 100% - your battery supplier will have told you if it comes with a smart BMS that is able to balance below 100%. Finally when you get back from a ride don't charge it until say the day before you next need to use it, as the battery will last slightly longer if not left fully charged & unused for several days. If you charge it on the day, leave say 15 minutes before using, to allow the battery to settle down.