How much is the damage likely to cost?

My own stupid fault, was reversing out of a shop and forgot the lampost was there, I did check before I reversed out but must have been in my blind spot

Kicked myself like mad, because lamposts don't just appear out of no where.

Depends upon how good a job you want.

Depending upon if the paint it down to the metal also.

A job so you'll never tell it was there at all and you'll be looking £300-£500 all in I'd say as very tops, but anywhere from £100 to £150 upwards depending upon where you get it done I'd say.