Where can i report Dells terrible service in uk?

its a civil debt ... you have to sue

Trading standards, they have to answer to them. Your local council has a department which is (kind of) free to use because that's why you pay council tax.

If you actually lived in the UK, you would ALREADY KNOW about Consumer Advice. I have never been further from the US than the Canadian side of Niagara Falls, and merely visiting Yahoo Answers, I can't avoid knowing about that UK government agency.

Check the MSE website as they have good information.
https://www.moneysavingexpert.com/shopping/consumer-rights-refunds-exchange/#pay

If you take longer than 30 days to return the item, you'll have to choose between a repair or a replacement. The retailer can veto either though if it's impossible to carry out a repair or the cost of a replacement is much higher than that of a repair.

Escalate it up their line of management.

Each time you talk to anyone, it should be done in writing, but if not, keep a file not of the date, the number, the name of the person you talked to and their position.

Go back to the last time you had a refusal or failure to perform. Ask the name of the officer, and the name of their supervisor and how to contact the supervisor.

Keep politely re-presenting the same facts, and if you get a refusal or failure to perform, take it up the next level.

You will eventually get a remedy, quicker than if you go via a third party.

Get a lawyer to threaten to sue, if you're in the right. If you're just whiny about something you're in the wrong about, you're not going to get shît, so be sure you're in the right here.