where can I buy prepaid cards with cash in uk?

I am trying to find a generally accepted anonymous online payment method and the one that seems the most promising is prepaid debit cards. They seem to be readily available in the US but I've been able to find very little info for the UK. I know i could use crypto for things that need hiding but i want to maintain general anonymity when buying from places like eBay, amazon and general online shopping.

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