More likely strategy and political decision-making. UK unis and Research institutions were knocking on Govt's door for months and turned away. Only relatively recently has the UK ramped up its testing capacity and that was when they brought the universities, and pharmaceutical companies like GSK and Astrazeneca onboard.
The UK is playing the long game and a conservative game. It may look bad now, but that's because in my opinion their priority is to avoid at all costs a 2nd wave in the Autumn / Winter. You can do that through immunity but maybe South Korea and Germany can hold it off through testing.
1 strategy involves deaths. The other doesn't in the short term but does it ever see you through?
On the positive side there's lots of activity going on with immunetherapy (not sure if that's a word) and vaccines (one got approved for a Phase II trial today)