I'm baffled, mostly because I have to do it in an underground carpark with 100% humidity, it sucks giant donkey balls.
That's where my squeek is coming from when driving along. I've replaced all the pads with bendix general CT (awesome daily driver pads btw) and I did notice a bit of intermittant drag on the rear wheels from the handbrake. Even though the handbrake doesn't do much until 4-5 clicks up and won't hold the car on a hill unless pulled up very hard.
So i'm thinking i'll get in there, clean out the rotors, check the pads, grease anything that should move and see if that fixes it

How do I actually get to the drums and what should I be checking. I have 'some' experience with drums but not a whole lot. I.e. are they supposed to drag at all when off? etc etc

I find when I did mine the hub was able to turn easily but you couldnt spin it freely as such. Remove the rear wheels, in the rotor there is a black grommet, remove that and the star wheel is in there, you move it up or down with something like a screw driver.

They should spin with no drag at all from the shoes. You lossen off the handbrake cable, adjust the shoes untill they just spin freely, then back them off a few more clicks. Do this on both sides then adjust the handbrake cable inside the car so it goes up 3-5 clicks with 20kg of force. Should be good enough to hold the car on a moderate slope with only 4-5 clicks.

Thats my method, here it is from the manual:

If the parking brake lever stroke is not the standard value,
adjust as described below.
(1) Remove the inner compartment of the floor console.
(2) Loosen the parking brake cable adjusting nut to the
end of the cable rod, to allow slack in the cables.
(3) Jack up the rear of the vehicle and support on jack
stands and remove the rear wheels.
(4) Temporarily install the wheel nuts so that the back
of the nuts contact the brake disc and hold the disc
in position.
(5) Remove the brake shoe adjustment hole plug, and
insert a flat blade screwdriver to turn the adjuster
wheel (to expand the shoe) sufficiently to prevent
the disc rotating.
(6) Rotate the adjuster wheel 5 notches in the reverse
direction to allow the disc to rotate freely. Carry out
this operation on both sides.
(7) Remove the temporarily installed wheel nuts and install
the rear wheels.
(8) Tighten the parking brake cable adjusting nut inside
the vehicle to achieve a 3-5 notch stroke of the parking
brake lever at the specified lever force.
Caution
If the number of brake lever notches engaged is less
than the standard value, the cable has been over adjusted.
Be sure to adjust it to within the standard
value.
(9) After completing the adjustment, check to be sure
that there is no play between the adjusting nut and
the pin. Also check that the adjusting nut is securely
held by the nut holder.
(10)With the parking brake lever in the released position,
turn the rear wheels to confirm that the rear brakes
are not dragging.
(11)Remove the jack stands and lower the vehicle to
the floor. Retorque the wheel nuts to the specified
torque.

Before I go ahead and do this, does it sound like the shoes are overly worn? they certainly feel it.
They do drag a noticeable amount if spinning by hand (it's an uneven drag as you spin the wheels) and like I said, it needs 4-5 clicks just to work, won't hold it on a hill unless pulling a lot more

Or is this likely to be something binding that needs grease/WD40 and then tightening further to make it work but not bind or go stiff and rubbish?
This could potentially explain my perceived poor fuel economy as well, finally.

spray the whole lot of the hand brake assembly with brake cleaner then hose out. 2 ways to do this, the lazy, yet effective way is through that hole where you removed that grommet to adjust the handbrake, spray the brake cleaner in there, spray, stop, turn the disc a 1/4 turn, spray, stop, turn the disc 1/4 turn ETC. then hose out with water in that exact same hole. the other way is to completely remove the disc, clean, reassemble. then follow instruction above to adjust handbrake

I would like to fully strip and clean them, it just doesn't seem obvious to get to them?
I.e. do I need to pull the brake caliper, hub and everything?

You'll need to remove the callipers (though you don't need to undo the brake line so no bleeding, just wire them up out of the way) to get the disc/drum off. From the manual (I've not dismantled the rears before) it looks like the hub might not need to come out to get at the park brake bits but I could be wrong. In any event, a visual inspection is probably warranted and calliper/disc removal generally isn't a bit deal. Make sure your shoes are adjusted in enough so they don't catch on the drum when taking it off and putting it back on and run through Jimbo's handbrake adjustment procedure afterwards.

To get into the starwheel which is how you adjust the handbrake you can do it through the grommet in the rotor, if you want to, dismantle the assembly to clean it all and reassemble it, you remove the calipers as stated above, remove the rotor (which can be fun due to sticking, so have some WD40 or Inox handy), once the rotor is removed you are there, once you loose the star wheel the shoe will be ready to fall off, just dont lose the pin that sits inside the housing near the starwhee,l as the hook that the handbrake cable pulls activates this, lose the pin, and then nothing will happen.

I had a quick look the other day when replacing pads but didn't see an obvious way to remove the hub though (by no means a thorough search). Once the caliper is off where is it held on, bolts in the rear? the only thing in the center is a strange looking metal piece, its got a tiny hole in the middle of it, and 2 flat 'blades'. Whereas on the front there's a nut to remove the drive shafts/hub. Does that center 'thing' come out first and expose a nut or...?

Why do you want to remove the hub??

If you want to get to the handbrake assembly you dont remove the hub, you remove the rotor.

Ok look at this photo.
http://i937.photobucket.com/albums/ad217/peaandham_bucket/IMG_5199.jpg (http://s937.photobucket.com/user/peaandham_bucket/media/IMG_5199.jpg.html)

The black subframe, with the green swaybar, focus on that. The rotors have been removed, the horseshoe thing you can see is the handbrake shoe, you can get to that by removing the rotor not the hub.

Once the caliper is off to remove a stuck rotor there are a couple of ways.

One is there is a couple of holes in the rotor that accomdate a bolt, you can thread bolts through these holes and it should push the rotor free from the hub/handbrake, however sometimes if you turn one bolt too much it will thread and cause a problem, so some people like the idea of spraying a penetrating fluid into the the gaps around the wheel studs and then giving the rotor a bash with a soft face mallet, try to avoid this but it does work.