"Unless you've already filed a flight plan which entails you flying IFR then VFR, to refile IFR after changing from IFR to VFR requires you to cancel the original plan and refile your flight plan enroute."
Do you mean that because you never landed (yet) the original flight plan will be open, so somebody will have to cancel it (is this possible without landing?) and then somebody else (a friend on the ground) will have to file a new one for you, sometime during the VFR section of the flight, which you activate with a radio call, a bit like UK pilots flying from farms get london info to activate their IFR flight plans.
I would not be doing this in the UK, no point. But there are interesting places away in Europe.
Maybe the biggest thing I didnt realise is than as soon as one changes from IFR to VFR the flight plan is terminated as far as the IFR clearance is concerned, and dumped out of the system. But it can't be completely dumped can it because you could fly a Y plan whose VFR portion crosses a frontier (say going to an airport very close to the frontier) and a flight plan is certainly needed to do that.