I can see you having a fair bit of trouble with the ebay advert.
https://www.ebay.co.uk/itm/185257936...4AAOSwGQJh4u~i
You do mention the damage grill, but often people don't really read things or even look properly at the photos. I can see you listing it quite a few times as people bid on the nice looking photo, then see the car with the damaged grill, the hole in the engine, see big bills in their future and walk away!
As for price......It's a bit of a hard one. There is a fair bit of work to do on it to bring it up to serviceable and whilst D2 S8's are getting rare and moving up in price....but to get top dollar they need to be in very good condition and original.
Having a quick look on the MOT check, the service history hasn't been the best, with lots of fails, so that may put the classic buyers off a bit too.
Here the specs tend to increase the price. Final Editions are often liked, though most dealers don't know what one is and say any Facelift car is a FE
Looks like there's an LPG tank in the boot, though no mention. This attracts some and puts some off.
Oh and for the most part private reg's aren't really worth much - I've still got my old S8 TNK one on retention from when i got rid of the car (4yrs), but have yet to find it worth anything in resale and New an S8 plate is like £250
Personally i'm a driver rather than a pride and joy type. I do miss my old S8 as it was a fun beast, which is why i occasionally skim ebay and ponder, though I can probably see myself going Tesla next when i have a decent budget and the second hand car market has gotten more sensible!