General ACCAInvoice for future services - Accrual/Prepayment - End of Month

Hello We received our company water bill dated 01/04/15 for period 1Apr/15-31Mar/16, which total amount includes 20% VAT. This invoice will be paid by (8) monthly DDs from May/15-Dec/15. As I monthly do all end of month postings, I need to post this invoice in our Sage 50 accounts system and also monthly DD payments. I was instructed to post monthly accruals of 1/12 of bill net amount: Dr Water Rates and Cr Accrual. Then clear accruals when DD is paid by Dr Accrual, Dr VAT and Cr bank. 1 - I have been researching and understand this bill matches with prepayment not accrual, and should be fully posted first to Dr expense, Dr VAT and Cr Sundry Creditors - then Cr Expense and Dr Prepayment - all these posting with date of 10/04/15. 2 - Problem it is as I am still studying the F2 module of ACCA4 level Business and Accounting, I do not know what to do next :-( 3 - I would be very grateful if someone could let me know how I should post the 8 monthly DDs and prepayments at the end of each month. Many thanks