Hi Mark, thanks for the heads up on the Nvidia defect forum. Good luck to you, also.

I find Sony's procrastination extraordinary and the unwillingness to even supply an address for a complaint is bizarre.

An update:

After some 34 emails and a 50mins phone conversation, customer disservices has finally conceded this is a hardware problem (because it occurs if the hard drive is disconnected - I told them this a number of times) but is so far unwilling to extend the warranty offer to this laptop even if the problem turns out to be the Nvidia defect (which I think we both know it is).  The repair is guaranteed for three months.  The details of the repair (reflow, reball, mobo replacement etc) can't be provided even hypothetically until the repair team have examined the laptop.  The repair will have a three month warranty. The minimum fee is 57 EURO / 49 GBP.

The ridiculous thing is that it has cost them more to procrastinate - they could have told me this within the first few emails.  And after all this, what confidence can I have in their repair?

I acquired the address of Sony UK's head office from the admin of the Nvidia defect forum:

Sony UK
The Heights
Brooklands
Weybridge
Surrey
KT13 0XW

A strongly worded letter of complaint (destined for the round file) and perhaps some legal action (looking into it) will soon be headed their way.

As for who will supply my future laptops... this has been a lesson for me to look at what people think of the supplier's customer care, not just value-for-money.

Thanks again Mark.

Hi Mark,

I should have kept this thread updated.  Sorry about that.

After another few emails back and forth with Sony 'support', here is the situation in short: I can have a 10% discount on the repair should I choose to go for it. 

I asked, hypothetically, if the fault is found to be the Nvidia defect would Sony charge me the cost of repair?  Sony's position is that if the laptop model is not on Sony's list of affected laptops (my laptop isn't on the list) the customer will be charged for repair.

"Kindly be  informed that in the case of all VAIO’s with these chips, extensive  investigations in cooperation with NVIDIA have been conducted and we  have found that a number of units are affected, and your model is not  found among the affected models. Therefore, the repair will be  chargeable."

Unfortunately I don't appear to have any legal grounds to challenge this. But other people should be informed that the "list of affected models" could be irrelevant to their specific situation - it doesn't in itself affect their legal rights, so they must not be persuaded otherwise.

Now, let's say the cost of repair is £150 - that doesn't seem an unreasonable guess (could be lower, could be higher).  It's guaranteed for three months.  So, for £150 I will get three months use; that's £50 a month.  But for £50 a month over 12 months, ie £600, I can buy a new laptop with at least a year's warranty (and six years 'warranty', in effect, under SoGA). 

Also, after this rigmarole I have no confidence in Sony at all:

• If they believed what they were telling me in emails and on the phone they are incompetent.
• If they did not believe what they were telling me they were being deliberately misleading - lying, basically (in my opinion, of course).
• They won't answer some direct questions, and they won't even supply contact details where complaints should be sent! Ludicrous.

With that in mind, and the fact that the repair will only be 'guaranteed' for three months, I think I'd be foolish to give them any more money.

I will buy a new computer soon.  I don't think I will look at Sony computers for a while! The really stupid thing is that had they been more reasonable in the first instance - acknowledging it is a hardware problem instead of being silly about it, for example - I think I would have accepted their point of view and not developed this negative perspective about them.  Never mind!  I am sure they have plenty of other customers.

This has turned into a bit of a rant again, sorry about that!

Good luck with your computer, Mark. nvidiadefect.com was a great recommendation, by the way.