correct me if im wrong but, if a worker isnt pulling their weight, all you need to do to keep within the law is give them a verbal warning, failing that, a written warning, still no change, then your within your right to sack them.
i recently started renting a round out, included in the agreement i stated, if they lose customers, they must replace them, if they fail to do this they have to hand the round back and pay me the 6 months equivalent of losses of earnings for each custies they lose otherwise court action will be taken. unless the custies cancel the service due to reason other then the quality of service.
this should keep them on their toes, of course im still new to this and havnt yet had the experiance of them messing up on me..........