Last December I paid £100 for supply and fit (into existing concrete posts) four wooden panels, each 6 feet long x 4 feet high. The concrete gravel boards were already in situ.
A couple of years ago, I paid £35 for resetting a loose concrete post. A tree branch had grown against it, and pushed it out of line.
I know these jobs aren't exactly what you're going to have done, but, since nobody else had answered, I thought that they might give you something to work on.