The simplest way to guard against it is by filing a flight level which is totally obviously decisively in controlled airspace
Doesn't always work
We cruised at FL410, but during descent into Farnborough, we were
cleared direct to a point, descend to FLx, Contact Farnborough Radar, You are clear of controlled airspace, radar service terminated
Then Farnborough Radar asked what kind of service did we require, without giving any options to choose from
There was nothing shown in the Jeppesen high / Low level charts that cautioned us about this.
It was the same on departure, we were given radar heading and altitudes, but not advised that we were outside controlled airspace and required permission to enter controlled airspace.
This thread was the only thing that i had read that prepared me for flying in UK airspace...... Thanks..
Mutt