I stick approx 350/400 a month into an 'annualised' account to cover tv licence, car tax, insurance, breakdown cover, health insurance, management fees, all the 'one off' anticipated items, makes it a lot easier to budget & you're not left short one month because of a couple of large outgoings (e.g. car tax & insurance).
As marksa says, if you opt for monthly or instalment payments many services will charge extra - car tax certainly does, as do some car insurers, Quinn Insurance do if you pay quarterly for health insurance (I think?) so TV licence may be the same.