.... the greater the gap between me and the edge of the road / kerb the greater the gap on my right hand side left by motor vehicles.
There is definitely something in this. My experiments have led me to thinking that the white line provides a phychological barrier that people do not want to cross. The other side of the line is for overtaking and is a danger zone.
If you leave enough room between you and the white line, drivers will try to squeeze between to avoid using the oncoming lane. In general the cyclecraft secondary position (the left wheel track) puts you in the way and forces people to start crossing the line, and once their seat is over the line, the more likely they are to move right over.
Caveats:
1) A minority of drivers will not move over, so will actually be closer the further right you are.
2) Some drivers take offence if you ride in the very centre of the lane. I think this is equivalent to riding two abreast in their minds. It's also a bit pointless as you are now riding closer to cars in the oncoming lane.
3) On wider lanes where there is room for a car and you, it is counter productive to get in the way. This really depends on speed limits and local situations.
There is no way to prevent
all close overtakes - you can only reduce the amount of them.