As a percentage of GDP, the UK has the 6th highest healthcare spending of OECD countries, on par with Switzerland. The UK is not an outlier in terms of spending.
Some of that is probably down to the dysfunctional models that have been brought in (in the name of 'cost saving' or 'efficiency' or what ever nonsense) - like Blair's PFI model where they signed up to pay £80 billion to private investors over the long term for what amounted to £13bn of actual investment... This seems to have continued under the Tories and the UK public are on the hook to continue to pay huge repayments to private companies for decades to provide services that could have just been publicly funded in the first place...