While I (in the wifes name though!) have the same car and engine, not had that problem at any speed (cough!!
).
You seem to have covered my first thought being wheel balance. Read in Auto Express that sometime the weight can sometimes fall off on alloy wheels.
You say that the dealer did the job and swapped the wheels as well.
Perhaps you could explain the problem to them and see if they are willing to for you to take it to a Independant tyre place to have tracking and balance done to see if they did it right the first time.
If not, then go with the internet opinion.
Oh by the way, hello

You seem to have covered my first thought being wheel balance. Read in Auto Express that sometime the weight can sometimes fall off on alloy wheels.
You say that the dealer did the job and swapped the wheels as well.
Perhaps you could explain the problem to them and see if they are willing to for you to take it to a Independant tyre place to have tracking and balance done to see if they did it right the first time.
If not, then go with the internet opinion.
Oh by the way, hello
