Dead and I do mean dead battery

[Sexual Chocolate]

Had the Elise sorn'd since September and its been on a trickle charger ever since. Well said trickle charger seems to have stopped working at some point and now there is noting left in the battery, not even the red light for the immobilizer is flashing. I attached another charger to it and there is still nothing (the light on the charger isn't coming on either). Is my battery completely knackered? Can I jump start it without causing any problems? Shall I just buy a new one? (Battery not Elise).