The times I have been closest to infringing a zone are when I have been routing back to my base airfield that is within the zone but ATC is too busy with people giving their life stories informing them about their latest problem with their Dash 8 indicating they will miss their takeoff slot or worst of all asking for the latest results of a major sporting event and I cannot get my request to enter the zone in. The few times I thought I would call up early and speak to the approach controllers rather than tower I get told to use a different airield instead. If you are concentrating on trying to get a call in you may not notice that you are getting very close to the zone. I have noticed that you do appear to get a better service if you ask for an IFR rejoin in preference to a VFR one.
One other thing to bear in mind with PPL traffic is we are usually single pilot ops and do not have the luxury except on training flights of the First Officer/ Captain doing the radio while we or the autopilot do the flying.