If something you buy is broken or not as described, you have 30 days from receipt to get a full refund. That is the law under the Consumer Rights Act 2015. After 30 days but within six months, the retailer must repair or replace it. If they cannot fix it, you can ask for a partial refund. This applies to everything you buy in a shop or online in the UK.
Digital content is now treated the same as physical goods. If a game crashes, an app stops working or a download is corrupt, you can demand a fix or your money back. The retailer is responsible, not the platform.
For used goods, your rights are the same. Secondhand items must be of satisfactory quality, taking into account the price and age. A ten year old laptop that dies after a week is not acceptable. Do not let sellers tell you there is no warranty on used goods. That is wrong.
Section 75 of the Consumer Credit Act gives you extra protection on purchases over £100 and under £30,000 if you paid by credit card. The card company is jointly liable with the retailer. If the retailer goes bust or refuses to help, your card issuer must step in. Debit card chargeback is not a legal right, but it can work.
One thing to watch: retailers often try to redirect you to the manufacturer for a warranty claim. They cannot do that. Your contract is with the seller. They must deal with the problem.
Know your rights and use them. The law is on your side. Paul