Dont think you can compare a Sheridan vs other .20 rifles like Theoben etc. Its a different beast.
In the Netherlands, therer isnt much .20 either.
Theoben was the first to really make those calibers for our market I believe. Now you can get HW in .20 too but why should you.
Most find their caliber of choice in either .177 or .22. Not much pellet choice either.
I wouldnt buy any .20 or I should be a rare Webley for collecting or anything