You pompus @rse.
Having used an installment plan previously it is reasonable to expect it to continue unless it is indictaed otherwise and when it is removed, to suddenly find that you need to pay ££ upfront, for families especially, it is a big issue.
Most of us pay our council tax monthly and would be screwed in they turned around in April and with no warning told us we had to pay upfront. No doubt, being an uber saver, you've that tucked away just in case as you're brill'.