iam, your problem is you live in the UK!
If you haven't dropped it, and it looks like a hairline crack to me (same as my hubby's MB) then I cannot see why they wouldn't fix it. It's in warranty and has only happened after a short period of time. If it was my MacBook I would go insane at them to fix it, especially after that short period of time.I spoke to the nearest official apple repair centre, and this is what they said.
Hi
Apple will not replace bottom cases in warranty, you can speak to Apple and
ask if they will make an exception.?
I, however bought my husbands MacBook 2nd hand and already had the hairline crack which as you know does affect performance so can't get it fixed.
One more reason why its worth it to go pro.
Sigh.
If anything has ever made me want to go PC its apples customer service.
Apple's customer service is much better than any customer service of a PC maker (dell, HP). This is one of the reasons that apple is so expensive. Don't throw in the towel yet, because we all know that Apple is a superior product.