Phone NHS direct, ask them for a local NHS dentist that can sign you up.
NHS rates are cheaper than private, or just pick up a phone book and phone places, try and get the cheapest you can.

some places do fillings for like £50, just for a basic metal coloured one, for white you increase the fee.

Numbing the pain works for only a short time, you live your life just trying to avoid the pain taking pills overy couple of hours, you will end up spending more on pills that it costs to go and get your tooth sorted.

If it was a toss up between - oh lets say a new intercooler, and my tooth sorting out, i would gladly pay for the tooth to be sorted.