Yes, either by cheque backed up by cheque guarantee card, or by cash but they can put a limit on what you can spend if you pay by cash.
I think you can we paid our bill with cash this year instead of card you can always phone p.o up.
Sailed from the USA so didn't want to put things on a UK credit card. I did submit my credit card number upon arrival. Went down every two days and paid my bill 'so far' with cash. Paid the last bill just before we left and they took my credit card number off my records. Worked fine. Was told "without a card number you have to pay 'up front'" and the fine print said 'no refunds'. Bear this in mind.