[ROVERNET - UK] More P6 B brake woes

[phing]

Hi
 I now have a complete rebuilt , re assembled,  braking system with :  a new master cylinder , rebuilt front and rear callipers ,[ 
all from Ruth, so they should all be good !! ],new flex hoses  rebuilt servo / slave cylinder by me using a genuine rebuild kit , 
new pads , new fluid . I also have lots of spilled brake fluid and  a head ache !! Our local Big Show takes place on Saturday , and 
I can't bleed the @#$%^%^^ ing system .!
The pedal won't move , unless I crack a joint . I've worked  my way out along the pipes ; from the master cylinder [ the one 
attached to the brake pedal ] cracking joints until I have vented air and dribbled fluid . I can get fluid , and pedal movement , 
through the servo/slave cylinder to the junction fitting with the mysterious " shuttle valve" . Then the pedal goes solid . I can't 
bleed fluid from the centre port which carries the pressure switch.
 What does this thing  do ? can it be stripped and cleaned ? Do I need some fancy device to keep the shuttle in place while bleeding 
the complete system from scratch ??
!
Cheers
 Patrick