The whole point is being able to look back and signal simultaneously to determine what is best for you. And for that you did very well. Many other cyclists would have looked and signalled as separate tasks and just maneuvered with potentially disasterous consequence.
However you need to remember your signal is a request NOT a command. You don't have any right of way when switching lanes. Bear that in mind when deciding to take it up with drivers in future. Yes it is annoying he accelerated but not as much as the discomfort you'll feel watching your back when passing that stretch for the next week until you forget about it.
@Vesalius
The whole point is being able to look back and signal simultaneously to determine what is best for you. And for that you did very well. Many other cyclists would have looked and signalled as separate tasks and just maneuvered with potentially disasterous consequence.
However you need to remember your signal is a request NOT a command. You don't have any right of way when switching lanes. Bear that in mind when deciding to take it up with drivers in future. Yes it is annoying he accelerated but not as much as the discomfort you'll feel watching your back when passing that stretch for the next week until you forget about it.