Firstly, I think a death rate of 0.5% is 5 times worse than flu. Secondly, your figures look very conservative to me, where have you got them from?
Worldwide, there have been 95,509 cases. 56,975 have recovered, 3,286 have died, giving a death rate of 6%. In time, when more data is available, the death rate might be estimated as a lot lower the 6% (we can only hope), but it doesn't make sense to have 4% as your upper end of the range including a margin for error. I can't see anything suggesting it's as low as 0.5%.
There probably aren't fewer that 100 cases in the UK.
Your two points are contradictory. If you don't know how many cases there are, by definition you don't know the mortality rate