Is it obligatory to give the other employee the full amount (216 pounds) that resulted from his effort in internal sales before the date of the new agreement on July 1, 2005, or should he be given a quarter of this amount, or does he deserve nothing, or is there another solution?

If your colleague at work cooperates with you voluntarily, or if his work is not essential for you, then you are not obliged to give him anything. And if you voluntarily give him something, that is good. However, if his help is essential for you, and he intends to be compensated by you, then he is entitled to the recompense for his work.