According to Jason Shafrin of healthcare-economist.com, only about 10% of British subjects have private coverage, which is basically the same as that provided by their National Health Service.  He doesn't specifically state the reason for that, but my guess is that most Brits can't justify the expense despite having access to better care and the reduced wait times.

You might want to talk to a different insurance agent.  HSA are meant to be used in conjunction with a high-deductible health plan.  The main advantage to this is that in a catastrophic situation, the maximum out-of-pocket cost works out to be less than that of a traditional health plan.  Many high-deductible plans cover 100% after the out-of-pocket maximum is met.