Getting smelly steam when I turn the temp up to max, which then won't clear as it's sort of greasy.

Checked the scuttle drains and they are clear, and no water leak inside the car.

 

I'm assuming the heater matrix must be leaking  - water level seems to be dropping slightly.

 

Is this a really hard job to do, anyone got a guide ?

 

 

I don't have a guide but I'm pretty sure it's dash out.

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A nasty, soul destroying job I'm afraid

mmm, radweld me thinks, and if that doesn't work, bypass the heater until Autumn, then think again !

Not a common issue Ive seen!  Is the coolant a nice pink colour and not discoloured?

Coolants fine, nice and pink, water level has dropped in the expansion tank, done about 500 miles so far this week, and it's lost about quarter of a pint -radweld in and fingers crossed !

Ouch - Just phoned my local VW specialist, £700 to do the job

Did the radweld do anything?

Unfortunately not, radweld seems to have slowed it down a little, but it stinks when the heater is on. Any way of cutting the plastics away to gain access without removing the dash (then silicone/fibreglass back up when done). The car's done 185k, nearly 10 years old, and I am struggling to justify such a large expense.  I haven't the time/skill to remove an entire dash..

Sounds like you need to by pass the heater and buy a coat for the winter if you don't have the time or inclination to do yourself. I don't expect it's a difficult job, just time consuming to get the dashboard out. You can probably carry on driving the car during various states of dismantling the dash. Just need to work methodically, a Haynes manual will probably help you gauge how much you have to remove.