As with all chokes, I wouldn't go thrashing about in them.
The first choke from Main chamber and down is pretty ok really, just follow the rope as it switches back underneath itself, then a short distance finds you in a squeeze down, then its across a sort of chamber to another squeeze down in the left hand wall. after this squeeze down your switching back again following that wall. this will very shortly take you to the 'airy' position above cornwall avenue (or the start of the way down into Fox chamber).
All of this is fairly normal caving really. but as you've just been through two squeezes i'd say if you had to be in a stretcher, you will probably be cold waiting for them to chisel you a way out.
Once in fox chamber as it flattens out your way into the second boulder choke is a hole (in the floor of boulders) on the left hand side of the chamber. from here if you've got your back to the wall your sort of going in front and to the right as you're descending into the choke, until you switchback and head back towards that left hand wall.
When you find the wall again, you will hug this (solid) wall round the back of the chamber, there are about 3 or 4 slots down (someone will probably correct me), but maybe in the right order these are a short climb down with a fat rope.
Followed briefly after by a climb down with some wood chocked across the climb and a thin? rope attached which leads down into the awkward squeeze/leg flail with a drop when you pop out the bottom (keep hold of the rope!), you'll know what I mean by leg flail when you're on the way out
Thirdly is another 'airy' or lofty climb down which gains you the chamber and the sump pool "this is the sea".
In short, the book says rescue would be impossible, i guess it depends on how long a period of time you would call impossible, anyway probably best not injuring yourself... I wouldn't want to be rescued from there if they've forgotten the warm blanket by accident.
As for movement in the boulders, I have not noticed any, but then I tend not to try and worry any of the boulders, they all seem perfectly happy where they are.