Please be aware that London has multiple airports and that these results are for all airports serving the city.
The best month to fly between London and Amsterdam is January and the most expensive month to fly is July. (Average prices, based on 715 datapoints.)
The best day to arrive at London is Wednesday and it would be best to avoid Monday, as prices are on average 56.85% higher than on Wednesday. (Average prices, based on 711 datapoints.)
The cheapest airline flying from London to Amsterdam is BA CityFlyer. They are 26% cheaper than KLM. (Average prices, based on 729 datapoints.)
The best time to fly is at around 7. (Average prices, based on 1191 datapoints.)