I have **tried** to use the split boot kits, but they never seemed to last long. I got them glued up OK, but the seam where the glue goes is quite wide and thick (stiff) so started to split itself after a couple 1000 miles. Mind you, they might have been improved, its at least 10 years since I tried to use one.

I persevered with the car for 5 weeks and then sold it.
I did around 1000 miles in it and never managed to hit 40mpg in any driving conditions.
In addition, the stereo system proved to be useless as well as it is set up for Japanese wavebands and cannot cover the full range of FM frequencies in the UK.
My dealer wanted around £400 to replace it with a UK spec stereo and change the dashboard housing.
I am very disappointed with the whole experience as it is a shame that Mitsubishi have been unable to deliver a car that offers the fuel economy it promises.
Perhaps, in the next year or so, on of the car manufacturers will produce a small 5 door automatic petrol car that really does deliver 50mpg fuel economy?
I hear there's a new Honda Jazz on the horizon.................perhaps that'll be the one!!??

April 2011
The following is my experience on my brothers Ford Focus.
It's a 2004 model, I can only relate what I saw here.
Downward pressure on the arm rest has to be resisted by the
teeth on the ratchet. Due to the length of the armrest, force
applied to the end of the armrest is magnified some ten fold at
the ratchet pawl. Most likely, the driver wants to turn round to
get something off the back seat and puts weight with his elbow on
the rest, probably right on the very end.
The armrest is stuck up in the half past twelve position.
The pawl is solid metal and quite strong, however the ratchet seems
to be of some light cast alloy and is brittle. At the end of the
ratchet is attached a piece of spring steel, there is not much material
between that and the last ratchet tooth, so the alloy fractures if too
much force is applied to the armrest. The spring steel breaks off also,
leaving no means of releasing the pawl, hence the armrest is stuck.

To get inside the armrest at the mechanism without removing the armrest:
The lumber support wheel should just pull off, according to my brother,
though I didn't actually do this. The end of the wheel shaft had split,
see later.
At the rear of the armrest, slightly underneath, was a black plastic zip.
The zip tag was tucked out of sight between the armrest and the seat side.
Use a small screwdriver or hook to pull this out and undo the zip.
Remove the armrest cover by peeling off from the back and then off the front.
Remove the foam rubber again starting from the back. Mine teared easily, but by tearing sufficient to just get it off the circular end and along the bottom it will slide off the front. Keep any bits as it can all be stuffed back later.
I saw three brass screw heads. Remove three screws, remove the side cover of the armrest. Now I saw the spring steel and snapped off alloy part. I see no way this can be mended ) unless you remake the whole ratchet bit, nor (because the bits are rattling about) am I able to work out how the ratchet works when using the armrest as described in the Ford Owners Manual.
There was a large diameter brass coloured spring tab washer used to hold the armrest in place on the metal shaft. This can be removed but gave me no advantage, so leave alone.
I saw the pawl and spring, I can now manually retract the pawl and put the
armrest down. Fortunately there were sufficient teeth left on the ratchet to leave it in a comfortable driving position. Refit the side cover, screws, foam and cover.
Try to remember not to move the armrest up.

To remove the armrest completely from the seat:
Pull off the lumber support wheel.
As mentioned previously, dig between the armrest and the back upholstyry to remove the large spring clip. It's made of wire, U shaped with squarish corners. You may be able to see part of the clip when looking down the hole where the lumber support wheel goes. I can, with a little difficulty, twist the white plastic inside the hole to adjust the lumber support. Use pliers to grip the wire clip and pull back. I can now get a largish screwdriver between the armrest and seat (blade held flat) and use it to lever the armrest off it's shaft. It will be quite stiff but once you find the right leverage point the armrest will wiggle off. I did not see any cables that
needed disconnecting.
As with all these things, once you've got the knack it'll come off in a trice.

Lumbar adjusting wheel and shaft:
On my brothers the end of the shaft had split so the internal teeth would no longer grip and turn the internal workings.

Repairs:
Ratchet - I didn't have long to study the ratchet mechanism as my brother wanted to get off back home, I see no means of repairing if the alloy metal has fractured, or of returning the mechanism to it's original method of working.
The best I could think is of attaching some cord to the pawl, drilling a few holes in the plastic and passing the cord out through the underside of the armrest. With a little knob or loop at the end to pull on, this will at least allow you to manually retract the pawl adjust the position. The original mechanism is a bit overcomplicated, surely a push button similar to a handbrake lever would suffice. But what do I know?
Lumbar wheel - the split end to the shaft may have been done by a previous owner, possibly by trying to force the wheel when weight was still applied to the seat back.
Here I got some very fine but strong nylon string, roughed the surface a little with sandpaper, a blob of Uhu glue and wrapped the string tightly round the outside. Bear in mind there is limited space for reinserting the wheel. A few turns of strong Sellotape would probably also suffice.
If you are able to find an armrest from a scrapyard, you need not buy the whole seat as you can just transfer your armrest cover over.

If you've tried all the above, please note. I had a problem like this on my Citroen after disconnecting the vehicle battery (the Pug is likely to be similar). After following the instructions in the owner manual for remote re-programming, the problem remained. I tried disconnecting the car battery again and leaving it off for a while, still no go. I gave up and took the car to the Citroen agent who (eventually) decided to download new code to the car. This fixed the problem. This may not be your problem but be warned of the possibility. If you go to a dealer, make sure they don?t start dismantling the dash looking for connection faults and blown fuses as my local dealer did?and charged well for it!

Thanks for everyone's help... problem now solved!!!

The handbrake cable had come unclipped and was catching on the tyre.... when I drove it, it must have been twanging the handbrake cable like a guitar string and it was no doubt springing back up and hitting the underside of the car!

Thanks again!