so I took my laptop back to a-mac utrecht, as its still got its crash-every-three-days problem. They refused to either refund the money or replace the laptop with a new one. Whilst they said they would talk to apple about a replacement, this has gone far enough for a product that was defective as sold, so I'm going to take advantage of the transaction protections I apparently get from the consumer credit act (and Visa), and dispute the transaction.
I got a lovely comment from the manager of the store when I said that I would expect a kernel crash every one to two years not every three days, that he would expect it to never happen. Which is funny in a "yes we sold you crap but we won't fix it" way.