Mick, UKBA has no interest at all in your day-to-finances or what you spend your money on or whether you have an overdraft or even if you spend more than you earn etc. They also have no interest in any savings you may or may not have UNLESS you have the intention to use savings in the application to fill-in any shortfall of income, or if you will apply on the basis on cash savings alone.

Cash saving alone with no income will require £62k
Using savings to make up any shortfall in the needed gross income of £18600 will mean only those amounts above £16k can be considered.