1. You can stop using swear words in the forum.
2. If you've "yelled down the phone at everyone at their help lines" I'm surprised you have had any response whatsoever. Rudeness is its own reward, and help-line staff aren't paid to be abused by customers - however irate said customers might be.
3. When you collect the next (and I hope final) replacement DO NOT leave the store until you have inspected it, and are satisfied.
4. Study the terms of your warranty carefully, and insist that PC World fulfils its obligations to the letter. Expect no more than that, and please try to avoid losing your temper - you'll be far more likely to get the result you're entitled to if you stay calm and collected.