It's a bit involving 1st time you set up to buy. You need to register and prove identity as the official platforms need to follow KYC. PayPal only does BTC in USA for now and you cannot transfer to external wallet, Revolut does it in UK but you also cannot transfer to external wallet. Coinbase fees work out quite expensive Bittylicous prices can vary a lot sometimes it's good, other times it's quite expensive and you get BTC straight to your own wallet so there is no need to do transfer and to pay Bitcoin network fee for transfer to external wallet. I use Wirex
https://wirexapp.com/ most of time. The prices are OK and often cheaper than Bittylicious but if you want to transfer to external wallet you have to pay network fee which varies depending on network load so sometimes it's cheaper to buy on Bittylicious, especially lower amounts. Wirex also has regular Visa Debit card that you can fill up with pounds and you get crypto cashback using it for everyday purchases. Monthly card fee used to be £1 but I think they got rid of the fee now.
I also use purse.io to buy stuff on Amazon using BTC with discount up to 33%, in reality it's more like up to 25% after the fees. For example if I want to buy something on Amazon for £100, I buy £100 worth of Bitcoin on Wirex, order stuff on Purse.io choosing 29-32% discount and will have about £20-25 left over which I keep as investment.