Due to my not avoiding an iron bollard which jumped into my path while reversing, I suffered a crack in the top cover (just under the Honda badge) and another in the rear bumper. Lived with it for a time, then decided to bite the bullet and replace those parts. Both jobs were quite straightforward, as described in Haynes. Removal of the handle cover involves prising out the trim handle (not easy) and you have to pull hard to release the 9 or 10 clips holding the inner tailgate trim. Try not to break them - my Honda dealer quoted around £2.50 EACH for replacements. On mine, the single bolt holding the left hand side of the cover had rusted tight, and had to be 'persuaded' off, so a good blob of Coppaslip was applied to the new one. The only other problem I had was releasing the wiring plug from the wiper motor; I know about the various locking mechanisms they use, but this one defeated me, so I just left it hanging, with no problems.
The bumper replacement was straightforward - once again you have to pull quite hard to release the side clips, and it's virtually impossible to release the four clips underneath without damaging them slightly, but I managed to reuse them all. All clips and screw threads were treated to a dob of grease or Coppaslip before replacement, so any future replacement (God forbid) should be easy The paint match is perfect, and my dealer produced both parts in two days, even though one had to come from Belgium.
The parts are not cheap; with VAT they cost me £320, but my 7-year-old Jazz is now immaculate again, and I just hope I can keep it that way.