You asked
Please provide any data/statistics looking specifically at (1) How many business people travel internationally in the UK and (2) which UK companies are the biggest employers of these people.
We said
Estimates of visits overseas by UK residents are provided by the International Passenger Survey (IPS).
There are estimated to have been 7,149,000 visits overseas on business by UK residents in 2015.
Note that this is the number of visits in total, including multiple visits by some people.
There is no information available on how many people made at least one trip.
There is no information available on the largest employers of UK residents visiting overseas on business.
You may be interested to see the latest annual publication, Travel Trends, which can be accessed via the following link; https://www.ons.gov.uk/peoplepopulationandcommunity/leisureandtourism/articles/traveltrends/2015