how would you do that on a sub £100 item?
Chargeback applies to credit cards and is particularly useful where the Consumer Credit Act 1974(CCA) section 75 is not applicable – for goods costing less than £100 for instance. Rules do vary between card suppliers.
Visa, for example, sets a 120 day time limit which starts from the day you are aware of a problem. In the case of tangible goods that you've purchased from a shop or online it would therefore be from the day you receive the items. In the case of something like flights, with an airline that goes out of business for example, it would be from the day the flight was due to depart.
The loading of the money to your PayPal account is considered to be the actual card transaction. If anything goes wrong with the loading of your account, you can use chargeback.
However, if the money that you load into your account is then subsequently used to buy goods and services, that transaction is not classed as a card transaction and is unlikely to be covered by chargeback.
If you want to ensure that chargeback will apply to a PayPal transaction, it's best to empty your PayPal account regularly so there is no credit balance. That way, when you make a purchase using PayPal the same amount will be debited from your bank account or credit card at the same moment you pay, making it easier for your bank or credit card provider to match the purchase with the debit.
