Nope they do not need a flight plan if VFR. Just do your normal thing at base and turn up. You are paying a significant amount of money for the handling agent to make sure everything goes smoothly. And if it does not make your you complain vociferously. I have had free handling on return visits at a couple of other places after complaining. Edinburgh charged me £114 quid for handling not to mention the landing fees etc. and why I asked for a taxi told me to call my own! I wrote to the MD of midwest pointing out I use them a lot and got a large credit.