A BCS-460 from embededcontrolconcepts.com would be a great starting point...(you still build the panel with contactors, SSR's, relays, etc) It incorporates PID in software, and also has dataloging and ethernet access (you can monitor from your phone/tablet/etc), you can watch the vapor and liquid temps, vary the duty cycle of an electric heater for a quick warm up then whatever %power your condenser can handle, shut off when a temp reaches a certain point, etc.. The forum has lots of helpful folks with experience in many different areas...
Obviously you would want to do the fail-safe and general good design practices, but the controller is a steal at less than $200, considering the intellectual property in it, and the cost of other PLC systems with PID control... Here is my brewery with the BCs-462 (next model up, but I would get just one of the 460's for each still) ...
When I get my DSP, this is what I will be using.-mike