BOF

Interested, yes. That's interested as in I'd like more info, particularly how you get on and what your opinion is after a few months, but I probably wouldn't go ahead with it unless something pushed me in that direction (and that just might be what happens after I clean up the existing EGR and see what happens then).

What sort of millage can you get out of them

At high mileages, with essentially any car, get a lot more concerned about the service history. You might get away with a rather spotty service history on, say, a 40 k miles car, but expecting to do the same at 100k+ miles is probably a bit adventurous.

Another interesting bit of evidence as to whether the car has been cared for is whether the previous owner has fitted decent tyres - Words like Pirelli, Dunlop, Goodyear, Bridgestone or Michellin on the sidewall are a good sign, but any name that you aren't sure how to pronounce, or looks like an attempt to rip off one or more of the above (Goodstone, for example) may be a sign of an owner who has been that bit too desperate to save money on maintenance.

Edge, titanium, zetec, giha, ect. 

Roughly, the order goes 

Edge -> Zetec      -> Titanium

                        -> Ghia

Edge doesn't have alloys (which may rule it out for many people, but is obviously easy to fix by buying alloys), front fogs and the dual zone, set-the-temp air con, and just has the simpler 'towards red for hotter, towards blue for colder' version.

Zetec puts those things 'right'

Ghia adds the Sony audio, bigger tyres and (rather delicate) different alloys. Better trip computer, but still with the orange vacuum fluorescent display (more info than on some of the lower models, although fittings seem a bit variable, so maybe an upgrade was possible). 

Titanium replaces the orange display with a 256 colour job (which is nice),  and goes up a step again in tyre size (...or is that just the Sport/Sport X?).

Various things such as the Sony stereo and the wheels could be upgraded by one step at purchase time, but as these were usually fleet cars, upgrades didn't happen that often. 

At the moment iv a st200 estate so im looking for somthing with a decence bhp an a bit sporty im looking at spending upto 9k MAX

I suggest that you look on, eg, the autotrader website for an idea of what is available and for how much.

Hi my 2003 focus randomly overheated a few months ago, i thought it was because I ran out of water ...

Aha, a chicken-and-egg problem: did the water leak causing overheating, or did the car overheat, causing a water leak?

...so I topped the car back up but 5 mins later it had drained all the water again. I limped it home and filled it up again I ran the engine for 20 mins monitoring what happens there was no leakage under the car or in the engine bay. It starts and runs but after about 20mins the water has gone and the car overheats and I have to refill it. Does anyone have an idea what the problem is?

Check the thermostat. It could easily be something else, but if it is the thermostat, at least the course of action is fairly straightforward.

Run the car on the drive, paying close attention as it starts to warm up:

i) Any leaks, even small ones, as it warms up?

ii) As it gets to the point that the temp gauge (and what is it doing during this time? anything unusual?) moves off the stop, it should be hot-ish on one side of the thermostat and cool on the other. Then, suddenly, there should start being water flow and the temps on the two sides being more even. 

iii) If the car boils over without evidence of water flow having got going (eg, top hose warming up) then probably the thermostat (or water pump) has a problem.

Well, I suppose if the engine exceeded  its max rpm, for some reason, the valves could float and some could hit the pistons.... It would still leave the mystery of why the engine exceeded its max rpm, but that would be plausible.