I have a VMach Stage 1 97k in 22, love that gun. Loooong ago, a mate of mine ahd a Venom tuned Hw80 in .177, that thing was awesome, the flattest trajectory I've ever seen on a sub 12ft/lbs air weapon.
I lived in Wales when I got my 97k, then moved to Scotland in 2005. 2 years ago here, air weapons became licensed, whether or not over or under the 12 ft/lbs limit. The AWC as it's known, is just as 'tricky', if that's the right word to obtain as an SGC or FAC. This prompted me to apply for my SGC, as currently owned air weapons would be covered by a valid SGC, so I still have my air weapons as well as a Winchester SX3 Black Shadow 12g, 3 shot semi auto. What a gun that is.
I did consider just selling up before I got my SGC but the gunshops here were just offering almost pennies for air weapons with the legislation coming in as there would soon be a glut. Many owners have decided to keep their air weapons and haven't gotten their AWC, so instantly criminalised themselves overnight.
You could try selling yours at a gunshop but you'll take a hit on the true value. Beware of posting to a potential buyer, it used to be allowed to sell guns via mail and mail order but that's been stopped and they have to be purchased in person, face to face in the UK.
Sound advice to get it on a chrono, if you're not sure of its history.
I think I would just keep it though (provided it's sub 12ft/lbs), it's a lovely gun, one of the best around in fact.