Was that £45 for just being on call or £45 if you had to do work during that on call ?
I'm of the opinion that an on call payment should be made as this interrupts your life style. When working say, a 12hr shift, and then going home to be on call for another 12hrs and to not be paid for it, means effectively you are always "at the beck and call of the company" but do not get recognised let alone rewarded. That is wrong.