htmlEncouraging discovery, after another few hours googling I found this excellent thread...

http://www.machsupport.com/forum/index.php/topic,20076.0

The guy modified a cheap HF start plasma by adding a ground wire to the tip thereby tricking the machine into thinking it is in drag contact permanently, this gave him full power plasma without hitting the metal and also cut the HF interference problem a lot.

its an inspired idea I think.

As it's starting with full plasma, could I then start my piercing cut at a more reasonable distance??

this needs experimenting I think....