I need to got to the dentist but cant afford it?

I have rampant toothache, I have not been to the dentist for over 9 years and have a fear of them like lots people. I really cant afford to pay hundreds of pounds in one go and suspect I need 2 or more fillings, how does payment work, can u spread the costs, do you have to pay anything immediately? With xmas etc i am very short on cash.