Yes, I believe the law and the way customs charges are calculated changed around 2021 when the UK officially left the EU. I'm not sure what the exact rulings are for importing other types of items, but with regards to blu-rays and DVDs, you won't get hit with any customs or VAT charges if the value of your package is less than £135 not including shipping costs.
I believe every online retailer abroad had to sign up for GB VAT if they wanted to continue selling to UK customers, which means that VAT is charged at the point of sale if you purchase less than £135 worth of stuff (although I never got charged VAT from what I could see when I purchased a blu-ray from Australia, so I'm not sure if some retailers pay the VAT themselves if under £135). There's currently no customs duty on DVDs/blu-rays, so there should be no extra fees to pay once it arrives in the UK. If it's over £135 then you'll get charged the standard VAT rate for whatever the item is (for blu-rays/DVDs, it's 20% of the total value including the shipping cost) + the handling fee from the courier.
So we basically have a £135 allowance for blu-rays/optical media before we start getting hit with any extra charges, which is honestly pretty nice all things considered.
I believe before this change, the limit was only £15 before VAT and other charges would begin to get applied.