Please be aware that London has multiple airports and that these results are only for Heathrow Airport.
The best day to arrive at London is Tuesday and it would be best to avoid Thursday, as prices are on average 64.42% higher than on Tuesday. (Average prices, based on 764 datapoints.)
The cheapest airline flying to London is Icelandair. They are 56% cheaper than KLM. (Average prices, based on 397 datapoints.)
At London the most flights depart around 20:00. (Hourly flights, based on 662 datapoints.)
From London it is on average the cheapest to fly to Paris and to Dublin. (Average prices, based on 211 datapoints.)
From London most of the flights depart to Paris, second best connected from London is Amsterdam. (Daily flights, based on 121 datapoints.)