Please be aware that Paris and London has multiple airports and that these results are for all airports serving the city.
The best month to fly between Paris and London is July and the most expensive month to fly is August. (Average prices, based on 233 datapoints.)
The best day to arrive at Paris is Monday and it would be best to avoid Tuesday, as prices are on average 84.76% higher than on Monday. (Average prices, based on 233 datapoints.)
The best time to fly is at around 7. (Average prices, based on 268 datapoints.)