Today I have successfully changed the heater matrix WITHOUT having the air conditioning system disconnected. It's a bit of a faf, but reasonably easy with a little care and some common sense!
The hardest part to get over is the air conditioning pipes sit behind the window wiper mechanism and also stops the unit being pulled straight out.
So, inevitably, some parts need to come off!
Everything I took off went in to a plastic Chinese tub. Then, things like screws don't get lost, and I know if I've put everything back on at the end!
Firstly, remove the wiper arms, the scuttle plate/cover, coolant expansion tank, the plastic strip that runs along the bulkhead, wiper motor/mechanism and finally the HCV.
This will leave you with something that resembles this:
On the left side of the engine bay, you will see a rubber mount (almost underneath the screen wash bottle top) which holds the two air con pipes. Pull the lower one out of the rubber, then from the plastic clip further along.
Also, I disconnected the electrical plug from the air con pipe. The other end of that wire was plugged in on the right side near the fuel tank evap purge unit. I unplugged it here also so I could remove the wire totally out of the way.
Remove the two small pipes from the heater matrix and remove the four screws which hold the black plastic cover (that the pipes come through).
Lift up the black cover, but at the same time, you want push the heater matrix pipes so they push through, leaving the matrix behind.
Now, deep breath because this is the 'iffy' part.... GENTLY manipulate the air con pipes so the heat exchanger unit can be pulled out but allowing the pipes to clear the bodywork above. An extra pair of hands at this point to help manipulate the pipes is a good idea.
After a bit of jiggery pokery, you should hopefully end up with something like this:
Phew, we can breathe now. We can see the lovely little heater matrix hiding in that dark hole. Pull the top of it forwards, towards the front of the car, then lift it out.
Out of interest, I had a look in the hole and found this:
Hmm, that's what has been evaporating and making my windscreen mist up!
It's easy to reach in there, so grab a hand full of kitchen roll and give it a damn good clean!
Put everything back together but in the reverse of removal, again being very careful with the air con pipes. Bend them too much and you'll end up creasing/rupturing one!
I took the opportunity to give the moving parts of the wiper mechanism a squirt with lubricant as they were starting to sound a bit dodgy.
When all back together, start her up and wait for the coolant to warm up. Pop the heater on hot and wait for the heat to come through.
A little squeeze of some coolant pipes may be necessary and don't forget to check the coolant level too!
So, total cost of this job £10...
looking forward to piks 
