Call function on a single page

Assuming your function runs generally, to limit it to a specific page use

if( is_page( 2094 ) ) {
    add_filter("sjb_job_location_filter_args","exclude_jobs_locations_uk");
}

The location of the function definition doesn’t matter.

P.S. Regarding excluding categories . . . yeah, we’d need to know a lot more about what’s going on with the called (plugin?) function