St Pancras International has 15 platforms. The visibility in the station isn’t very good as it is split between two halves. Half are underground (platforms A + B) which is operated by Thameslink. The other half is above ground. Platforms 1-4 are run by East Midland Trains which you can see Eurostar from through a metal railing. Platforms 5-11 are run by Eurostar which you can’t get to without travelling on one of their trains with a valid passport. Finally platforms 11-13 are run by Southeastern railway which again you can see Eurostar through a metal fence.
Thameslink common classes are class 700’s.
Eurostar common classes are class 374’s and 373’s (which is basically the only two classes Eurostar owns).
Southeastern railway common classes are class 395’s.