I got a reply!
Dave Malherbe from Acer South Africa called me, and after a chain of "returning your call" voicemails, we spoke yesterday. He told me that my request has gone up the chain of command at Acer HQ in Europe, all they way to the President (or at least his PA), and he'd been authorised to give me a discount on my repair.
He could drop the cost from over R6 000 down to around R4 400 (+VAT). Not much of a discount. For something that escalated so high, I wasn't very impressed. I said that I'd rather get it repaired in UK (if you factor in courier costs, it's still cheaper to send it there).
We then discussed my extended warranty, and he said I'd need to pry it out of Easy Computers (my supplier in UK who'd sent me the wrong laptop). So I fired off an e-mail to them. It's gone backwards and forwards a few times, and they told me to contact Acer again. So I sent a very strong e-mail back to them:
We are sorry you are experiencing technical difficulties with your goods. All manufacturers have dedicated support lines staffed by trained personnel. We strongly recommend that you contact the appropriate manufacturer of your product:
I did that. Over a year ago, in fact. And they did nothing. Eventually, this week, they told me to contact you guys, as you didn't supply me with the extended warranty pack that I paid you for.
If this is going to be a problem, please speak to my Acer contact who I've been dealing with: David Malherbe +27 11 233 XXXX. He knows all about my case, and if you mention my name, he should know who I am. He says that you guys need to supply me, you say they need to supply me, please can your sort it out between yourselves.
I spoke to Dave again, this morning, and he offered me an even bigger discount. If I didn't want my motherboard back, he could discount it to R1 999 + labour (R250) and VAT. That's starting to sound reasonable. I still think I should get it for free, but I'm almost prepared to pay that kind of price, just to save myself further hassle...