Would anyone know if this bus picks up at any other London station other than Victoria Coach Stn? If so, which station would be the closest to the Eurostar train station?
Earls Court or Hammersmith? I believe that from any other National Express stop you would have to change at Victoria anyway, and there are much quicker ways of getting from St. Pancras to Victoria - on the Tube it's Victoria line southbound from Kings Cross-St. Pancras to Victoria railway station (14 minutes at peak times) then a 300 metre walk to the coach station.
Starts at Victoria Coach Station, collects at Heathrow; no other London stops.
The only other stop that is loosely in London is at Heathrow, on the slower services. The faster ones only stop at Reading and Swindon. Timetable: http://www.nationalexpress.com/assets/uploads/pdf/timetables/403.pdf Rail connection might be a bit easier than coach for this journey IMO.