1. Consult with others!
If you work for a global corporation with a presence in London, contact HR for additional information. The same is true if your institution has connections with local businesses (they always do). Send an email. Call. Demonstrate your curiosity. You won't receive if you don't ask. What's the worst that might happen? Also read: 7 Brutally Honest Truths About Your Abroad Internship!
2. Look in the appropriate spots
There are several options available depending on the sort of work you want. I'm often surprised by how many individuals rely entirely on employment agencies to get them a job, without putting in much effort themselves.
3. Maintain your modesty
I used to recruit elite people for a large worldwide store, and nothing impressed me more than humility. Never, ever confuse humility with a lack of self-confidence. The former is necessary if you want to succeed in London (or anyplace else), but arrogance will get you nowhere. So, be modest not just in interviews but also on your CV.
4. Be unique.
With hundreds upon thousands of newly graduated university students each year, it will be difficult to distinguish out. What you can do is stand out. How? Does this describe you? I'm not advocating you go to that extreme, but utilize your imagination to ensure that your CV and presentation letter remain in the recruiter's hands for longer than the standard 7 seconds. If you are from another country, you should emphasize your cultural distinctions (languages spoken, larger cultural understanding, etc.) rather than hide them.
5. Put forth the effort
When I traveled to London for a three-month internship with one of the largest management consulting firms nine years ago, my manager summoned me to her office for an evaluation and discussion about the future. She was a forthright lady who was not afraid to harm others. She told me exactly what she was thinking. "Your English is still fairly awful, your clothing are from H&M rather than Prada, you don't stand out for exceptional speed, but you work harder than anybody and make up for your deficiencies by putting an unbelievable amount of energy and enthusiasm into what you do," she informed me. She offered me a permanent position in London at the conclusion of our discussion, when I was practically in tears and certain that my internship and UK experience were coming to an end. So, pay attention to Auntie Sabri and work hard. More difficult than everyone else. And outperform the competition. That is the finest advise I can provide you.