I don't think it's a case of evicting without grounds, I think it's more a case of nipping a potential problem in the bud. If it can be done within the law then I think it's in midsummer's best interest. This forum is after all called Property Invesment.
As for the agent thing. We initially used a big agency. Big mistake. Since then we've used a single agent who left a big property company to go it alone. I met him through work (during our time with the agency) and he is a star. Charges less than the agency, vetts the tenants and we've never had a problem. He also manages the property and deals with any issues the tenants have, usually within 24 hours.
Since we employed this agent we have not spoken to or dealt with any tenants directly. We do have final say over who moves in but base our decision on the agent's recommendation. We've had no complaints from the neighbours about any tenant and the property is in better condition now than when we let it!