Assuming a 3% APR on your �3,600 would net you interest of �108 at the end of the year (or just under 30p per day) [3600 x 0.03]. It is not quite as simple as that in terms of daily interest, since the 3% is an Annual Percentage Rate � if you were to work out the daily rate, you would need to take into account that after each day � the added interest amount, increases your capital sum.
But as a general guide, you can blow 30p per day, knowing that your ISA savings will cover it at the end of the year - enjoy.