I took my first ever trip on the Eurostar, to travel to Disneyland Paris on the direct service which sadly is due to end in June.
Check-in
For the journey they had a separate queue for the train, where you first scan your boarding card and then go through security similar to an airport.
Following this, you then go through the UK Passport Control followed by the French Passport Control.
You are then in the waiting area, boarding began about 20 minutes prior to the trains departure.
On Board Service
I was in Standard Premier for my journey which gave me my own seat, and for the journey to Disney they give you a crousint, strawberry youghurt, apple juice, water and a choice of tea or coffee.
The seats were very comfy with good legroom although if you wish to recline your seat, the legroom isn’t the best for tall people.
The staff on-board were friendly and welcoming during the service.I
If you wish there is also a cafe where you can get some drinks including alcohol and some snacks.

After arrival you simply walk out of the station and you have arrived at Disney with no need to show your passport since you do this before you leave London