I keep asking about where to find Flat share agreements and keep being told use an AST

Tenancy Types and Management

Hi again, I'm trying to find an agreement for house / flat share (non resident landlord) and keep being told to use the AST provided. I don't want an AST because I have to wait 6 months (even if I make the agreement shorter (ie 2 months) until I can get rid of problem tenants using section 21 accelerated procedure. Can I issue notice to quit and get rid of a problem tenant in 4-6 weeks, as I can with a House / flatshare agreement if I wish to. Please please help, I don't want to have to wait 6 months while a tenant sits in my property not paying rent, or being a nuisance..... what can I do to an AST to be able to do so.... OR, where can I get a agreement I can use so???