The Osprey is a doddle to smooth out.
First, line the piston with a sheet of aluminium cut from a drinks can, but leave the cocking slot clear to avoid the cocking shoe rubbing against the sleeve and wearing it out (if you don't leave the slot clear you will get slivvers of ally being ripped off the sleave, and these can find their way inside the gun). Next, replace at least one of the piston rings with an appropriately sized O ring. If it has one of those f+*&in9 horrible square section mainsprings fitted, bin it, replace it with a standard one, find the original owner and slap him for fitting it
If spring guides float your boat, you can either get a delrin one made up which wedges between the spring and the back block, or have a "floating" one made that just slides inside the spring.
My own .22 Osprey shoots very smoothly with the lined piston and an O ring fitted, and I have a Hawk MkII that shoots nicely that I did all the above to, including the floating spring guide. You'll never make them perfect, but the shooting characteristics can be improved.
The South of England has 2 good things, the M1 and the A1. Both will take you to Yorkshire.