I'm not up-to-date on British financial terms, but as I understand it "booking a charge" is the same as "arranging a loan" or "agreeing to a letter of credit." It's a vehicle through which an entity can borrow money, but it is not itself the borrowing (or drawing down) of these funds.
Any business that expects to receive a significant portion of its turnover in May but has expenses from now until May will book such a charge/loan/LOC to make payments if present cash is less than future expenses, and then will pay off the loan at the end of the term from future proceeds.
It doesn't look to me any more complicated than that; this seems to be a normal business practice. As ESK has suggested, this could be a financing structure to arrange a large transfer (more hopeful than me, I admit), or as I've suggested it's simply a structure to bridge the gap between everyday expenses (for 10 months) and receipt of the PL broadcast funds.