.20 "slug" pellets

[angrybear]

I've never seen or heard of such a thing in the UK, there may be companies that make them but that doesn't mean they get imported over here.
You'll probably need to speak to the importers to see if anyone brings them in.

I'm also struggling to see the point obviously you'd need FAC power due to the weight and if you have the FAC then .22 or .25 make far more sense than .20

It is at sub 12 that .20 has it's place as being a harder hit than .177 but without the weight of .22 to effect trajectory too badly.

[Rapidnick]

The closest thing to what you want are the Defiants which are sausage shaped.
Can I ask why given the difficulty of finding a good .20 pellet you want to make your life even more difficult?