To catch a train before 09:00, you would need to board the 08:19 from Waterloo - which would get you into Paris by 11:47.
Eurostar
Yes
the Eurostar arrives at London Saint Pancras.
London Paddington. Catch a train heading for Bristol Temple Meads.
Eurostar from Gare du Nord
London St Pancras International - Paris takes about 2hr 15 min
Glasgow/London/Paris 7 hours 36 minutes
You can't travel directly from Gatwick to Paris by train. You will have to take a train to London St Pancras and then get on another train to Paris. Unbelievably, you can't fly from Gatwick Airport to Paris either.
Yes, a train to London and then get a connection to Paris via the Channel Tunnel
The Eurostar travels between London and Paris, and between London and Brussels. It does not travel between Paris and Geneva.
Euston