Data taken from UK government dashboard
Note 1. This assumes everyone with/without the virus is equally likely to meet, which is likely not the case (so probabilities may be lower)
Note 2. The ONS recently estimated as many as 1 in 50 people have the virus - equivalent to 2000 in 100,000 (so probabilities may be higher).
Note 3. Stay at home. Wear a mask. Get the vaccine.