Bottom line - don't do what you're supposed to - ie. report it to your insurers. At least, not at first.
First thing to do is consider what your insurer's 'approved' (ie very expensive) repairers would do. My car received a ding in the supermarket car park while I was inside doing the shopping. I thought it was another vehicle, but a later check revealed the damage to match the height of a trolley. So, I initially reported it and discussed it with the very helpful lady on the phone and my neighbour, whose garage does my servicing. Wing was dented and bumper scratched. They would: remove wheels (and maybe suspension for 'better access'), remove bumper, remove light assembly and wiring, remove wing. Supply new wing and bumper and spray to match, then reassemble everything. Garage estimate - many hundreds of pounds = write off car.
Checked on ebay. Matching wing available less than 20 miles away, £32. Even better, matching wing, plus two doors, £50. (Plan was to buy these, sell the doors later at £50 each). Tools required - socket set and a couple of screwdrivers. Time to swap - around an hour. In the end, as the scratch on the wing hadn't exposed any bare metal, I decided to just leave it and wear the battle scar.
So I spoke to the same helpful lady at the insurers and got them to cancel the whole thing, and send me a written confirmation that it would not affect my NCD or future premiums. They did. When renewing insurance the next year I changed company and duly informed them of the incident, as you're supposed to (and it was indeed logged as a no-fault incident with no claim made) and they said it would not affect the premium - it didn't.
My son and I share an MX5. Our standing joke is that it's used for target practice, as it's been bumped into six times while parked (twice by a rather embarrassed neighbour!). We kept quiet!