Increased air activity over Kent

Around 2015 I noticed a sudden increase in air activity over north Kent near Maidstone,
while it is not unusal to see commercial jets over the area there was a number of smaller looking jets flying much higher and one large twin prop plan flying in a south west direction.

Is there any sort of air show happening this week or is there any other reason that people may suggest this sudden increase in small jets and possible airforce plane/s??