OK, an update from me.

1. Checked the offending leaky location and would you believe it - swimming pool of water under the battery.

2. Groped around for the holes underneath to unblock the gunge plugging them and could not reach them - So you can reach them in a standard car, but once you've got all the spaces filled with vegoil heating parts and hoses it's gets a bit tricky.

3. Used the quick and dirty release of water method. Pushed up the grommet that seal around the heater matrix hoses from underneath. This allows the water to drain away. can be done at any time by anybody finding water in that compartment - PLEASE DO THIS if you don't have time to remove the battery. Will still need to take the battery out and open up the holes further at the weeeknd. Perhaps I'll get a drill in there and do the job properly.

4. followed this guide here from Ginge. found exactly the same problem. Cables poorly connected in the factory wrapped in sopping cloth tape sitting in a pool of water. This reminds me of the bank adverts. Surely nobody could accidentally design such a ****** set of circumstances. A quick look showed that two of the cables had corroded away. Stripped and repaired the cables with spade connectors and all is now working.

The above took less than 1 hour. How can VW possibly be charging £800+ for this work. This has to be one of the biggest scams known in the British car industry. Even if you manage to get a price reduction following a massive arguement you're still paying many hundreds for 15 minutes work by somebody who must have done the same repair job thousands of times! I recon Watchdog should hear about this (if they have not already)