news.sky.com/story/covid-19-supermarkets-most-common-exposure-setting-for-catching-coronavirus-in-england-latest-data-shows-12136418
So according to this article number 1 is supermarkets and in second and third place are secondary and primary schools. Care homes are right down the list alongside hospitals.
Care home and hospitals are where the most restrictions are currently in place. Appears to me that the more restrictions in place the less exposure.
Definitely very true in my tier 3 area (Yorkshire and Humber) which is currently the worst hit area in England.