Eurostar is much nicer than a plane
As a student I had a research trip to paris for 7 months, and found the train much more useful and quicker. I did not have a car, so could not drive, and parking in London/Paris is a pain, and expensive.
The plane worked out as this (using Charles de Gaule).
Central London->Heathrow/Gatwick (1hour, conditions not possible to use a laptop etc.)
Arrival before your plane leaves to permit invasive security checks (>1hour)
Plane flight (~1 hour)
Collecting baggage (30mins @ Heathrow, 20 at Charles de Gaule)
RER [Tube] to Central Paris (Gare du Nord station 1 hour)
Continuation to accomodation (25mins)
Total trip (at best): 5 hours, and it's all broken up into small sections.
contrast this with the Eurostar:
Central(ish) london to Waterloo (as it was then): 30 minutes
Arrival time before train needed to leave: 40 minutes (in reality you could turn up just on the 30 minute deadline, and it's only 10 minutes if you have a first class ticket [did not buy those though])
Travel time to *central* paris, Gare du nord: 2h35
Travel time to accomodation: 25 minutes
Totalling that up we get 4h10, and you have at least 2 1/2 hours of time to work/sleep/look out the window at a changing countryside (apart from 1/2 hour of blackness in the tunnel). On the basis of that and that you could generally bring in much bigger luggage items, the Eurostar was a winner.
If you live near Luton airport (no I'm not calling it London by any hope and a prayer that the airlines want to call it such), then flying might be better, but given the journey is so 'bitty', I much preferred the train; it's much more relaxing as well. 2 1/2 hours of sleep was really handy at times after a tiring visit to London. That was not possible on the plane