They're often called "lifetime fixes" or "fixed for term" in the UK. You can easily get them. The term customers choose is typically 25 years rather than 30. However they are currently running at an interest rate of a little under 4% which is much higher than the rate offered on a typical 5 year year fix. This makes them unattractive when you can just perpetually keep re-mortgaging on 5 year fixes.

You can absolutely have a 30 year mortgage that is fixed all the way through. It's rare that people take it though, most opt to 5-10 years fixed with variable late afterwards from my own experience (Austria). The standard product used to be fixed rate.

In France 99% of mortgages are fixed rate, for the entire term.