RAPA,
you said:
We were given line up and take-off clearance after 40 seconds.
this gave me the assumption you were not on the runway yet.
Be aware that even a 2 min separation between a "light" 738 at about 64 to behind a "heavy" 321 has to deal with some interesting aileron inputs and my coffee does not stay in the cup....
You mention 15 - 25 seconds to rotation....never achieved this in any turboprop I flew, and that was the Cheyenne, Metro, Saab340, F27.
In a situation like your one behind a jet, why not slow down a bit and make life easier for you and others. Smooth line-up, smooth adjusting of thrust, and your 2 minutes are available.
Fly to Paris, any airport....
Fly to Stansted in CATIII....
Separation is today at the limit during certain times of the day.
Get me right, I do not think that the separation you were provided with complies with any safety aspect, but bean-counters find it safe. And they make the laws.
Sentences like: Limits are there to be reached, not to be observed.