Two things will have an impact on its value...
As an used Omega, with no Mot, limited history and 5+ owners, it will be worth around £1-300 depending on the state of the bodywork...
As an investment, with only one owner, pristine bodywork, garaged and polished its entire life, every receipt from the day it was ordered, freshly serviced and Motd with absolutely no marks or scuffs inside, it could be worth £3-4,000. With one caveat: that you can find a buyer. Well restored Police Omegas are already appreciating staedily
Omegas will eventually appreciate and the only ones worth preserving are those that have genuinely been cherished their entire lives, even then, your potentially looking at a 5 or so year wait.
If it were me, and I had somewhere dry and safe to store it, then I would jack it onto axle stands, cover it up and leave it until I lost the storage. Then I would approach any local specialist dealers, and offer it to them as a modern classic. The problem that you have is that 80,000 miles, whilst not high, is perceived to be more that people would like for a modern classic.
You could shop around locally for such dealers now, if you're keen to sell it on appraisal rather than simply popping it on Gumtree etc... equally gather all the paperwork, get the car looking a million dollars, a high quality valet would be £100 well spent, then on a nice , bright day, get several good pictures of the car... ebay only allows 12, so choose those ones carefully, but take pictures of everything, including all the nooks and crannies and link to the album in the advert, so that people can see how clean the car is for themselves. Then place a classified ad on ebay in the classic car section with a price you see reasonable... £3,500 or offers would do it if it's genuinely outstanding/owned from new etc... prepare to bide your time and eventually someone will buy it.
If, however, you want it sold quickly expect to see it gone for a relative pittance.
And whatever you do, don't put a price on here until you've enough posts to legitimately advertise here, or else it will be deleted. Limit is currently 250 posts, so get stuck in and you'll soon be there

You could start by posting some pictures in the gallery section, but I can not reiterate enough that you make ABSOLUTELY AND CATEGORICALLY NO mention WHATSOEVER of the car being actively for sale and no mention of price or links to your own adverts
