Julian, I am not sure you would knock off the FAA IR in just 2 weeks if you have zero instrument experience.
I did it in two weeks however . . .
1) I had done a lot of self studying before I went out.
2) I had passed the FAA Instrument written before I went using some excellent software from
Dauntless Aviation
3) It was hard work and most definitely not a holiday.
I agree that if you just rock up in the States having done no preparation, to do it in two weeks would be almost impossible.
Julian