Update.
Had the Airking at the range today with the Pro Air scope, Dampa mount and JSB Express 4.52 pellets.
Reduced the distance to 25 yards and pretty quickly I was achieving 8mm groups.
I've now put approximently 600 pellets through it and it appears to be settling down nicely.
Still not easy (for me) to cock but I'm adapting. However its really great to shoot !
No regrets, I love this air rifle !