Thanks for the suggestion. I ended up jacking the car up at the front and locating the thick main alternator output cable which runs low enough to be able to reach with a probe. I used a long metal sharp pick to piece a tiny hole in the cable and then clamp on my 12v starter pack to the other end of the probe. The electronics sprung to life and I was able to press the unlock button on the key as I lay there under the car, juggling everything and wishing for a third hand!!!
I’ve since removed the driver’s door barrel, soaked it in wd40 and I’m pleased to say that it’s now turning freely when the key is inserted. To top things off I’ve ordered a new lock mechanism for £75 because of the usual vw micro switch issue… have they improved the design at all in 12 years? They didn’t between 2004 and 2011, the period between me last working on VWs.
Frustratingly, the mechanism within my door is not the type that is readily available from third parties and eBay etc. it’s a different type which I was only able to source as a genuine part: 5N2837016C
not sure why the difference or why the part changed, but the micro switch design/quality is still just as bad as the previous generation 😄 How I miss the days of a plunger switch in the A pillar, or in the B pillar like still used on my modern Japanese car.
Anyhow, thanks again for taking the time to try and help.