I restore C19th shotguns for a living and have dealt with several Coggy's over the years. Many dealers won't touch them but this is based on the old English guntrade belief that machine made bad, hand made good! They are not bad guns but a bit quirky inside, some of which is a bit sub-standard but nothing that is going to worry a user, just an offence to the gunsmith!
Sleeved (not re-sleeved, that would be a sleeved gun that had been sleeved for the 2nd time!) guns are usually worth considerably less than a gun with original barrel (2/3rds, all things being equal) but may make it more user friendly, eg 2 3/4" chambers, better chokes etc.
Sale value is a factor of its barrel condition (state of proof and minimum wall thickness), aesthetics and practicality.
The first criteria is impossible to ascertain without the right tools but is a matter of legality and safety so you are going to need to find a friendly gunsmith who will measure it up for a small fee.
The second and third criteria are for you alone to ascertain.
Sale value?
If the barrel measurements are legal and good, then £300 to £750 depending on how well it suits your specific needs.
If the barrel measurements are illegal (out of proof or minimum wall thicknesses below 0.020") than walk away.
Remember that selling any Coggy, let alone a sleeved one, is nearly impossible unless you happen to trip over one of the very few people who want one.
Finally, S/S shotguns are very much on the slide, O'U's rule the sales roost nowadays. I hate it but it is the truth.
I ALWAYS shoot with a S/S, many friends have asked me why.
I always say 'I prefer to miss in style! And when the wheels fall off, I can always gaze at a beautiful piece of craftsmanship!'