Its probably some legal way round the law for loan sharks, probably legal to sell vouchers but not lend you cash
If you want it save for it, if you cant afford it dont buy it, only good credit is interest free credit as long as you DO pay it off within the time scale, keeps your cash in your account a bit longer. same with credit cards, use them to get your points/airmiles or whatever and pay it off within the 28 days.