I am Pakistani passport holder and having visit visa for the UK (still 4 months left to end). I am back in Pakistan and going to apply for a Schengen visa. I want to ask that can I still travel from France to London and where will I see immigration? and where will I get stumps for the exit? for example, I am getting a visa from swiss and then want to travel from France to London on my UK valid visa.
Your visas will be valid for your journey into and out of Britain.
Passengers travelling on Eurostar trains from Paris pass through both French and British immigration at the Gare du Nord in Paris.
Travelling from London they pass through British and French immigration at St Pancras.
There are no immigration formalities on arrival in either direction so your passport will be stamped at the station you board the train.