Postals
Yes, there are postals run by the NSRA, and also very good ones run by the Dorset association, but from your basic questions I suspect you may need to resolve some of the basics, such as all air target shooting is with 4.5mm, the best bet is to join an NSRA affiliated club, the "club finder" from the NSRA website will help you wth one in your area or even phone them to ask as all clubs are not on the site.
Good shooting
Robin
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?