We have just had the same experience mid-Channel. We heard some distinctly non-Euopean VHF chatter and were then passed by a container ship that was outside the shipping lanes, going at high speed and smelling very peculiar. We then had an infestation of 3 different types of insects in substantial numbers. There were: 1. Bog-standard flies 2. Mosquitoes which contained mammalian red blood (hopefully not ours) 3. Wasp-like insects of a distinctly non-European type.
We crossed the Channel on 2nd July, so this is probably the same consignment of fruit (?bananas) that went past you on Tuesday. Like you, we couldn't remember if insects could fly cross-channel distances.