Am I able to pay the deposit on one card then when i've saved up enough pay the rest off on another?
yeahAre you talking about the Finance option from Hitachi?
yeah
Am I able to pay a monthly sum for so many months for the duration of the 12 months or does it have to be one big sum?Whichever account you use for the deposit will be the account linked to the agreement.
you may be able to change that by calling Hitachi directly and discussing with them.