There was no exponential growth in Covid-19 infections the UK. From the first days of the outbreak growth rates were in decline.
The following chart produced by financial strategist Alistair Haimes should put the above question to rest (compare it with the above chart).
The left hand side starts in March 2020 when the UK had had its first 300 infections and then stops at 10 April when Europe as a whole had reached a growth rate of zero or less. The chart is analogous to the above chart of interest rates. If you cannot distinguish the different colours and European countries don’t worry too much (UK is dark blue) as they all show the same overall pattern. The trends are all downwards, from start to finish.