This is easier said than done.

Most developed nations have all kinds of barriers and quotas in place to make it difficult for aliens to fill jobs that might otherwise be filled by citizens.

Sometimes the right connections, company sponsorship, etc. can get you in; but if you're imagining just flying to the UK or wherever and getting a job, that's not possible. Even if a company there wants to hire you and is willing to jump through legal hoops it still may not be possible.