If you are European, it probably does not matter what qualification you possess, or even whether you possess any qualifications at all, you will get job that you want (particularly if you are in London and are a European from Australia, New Zealand or South Africa).

An MBA in Marketing from a credible business school would probably do harm, but as previously advised by someone else, the Chartered Institute of Marketing are probably best advised to assist you.

Note that a number of leading Jewish businessmen such as Alan Sugar and Philip Green possess no formal qualifications whatsoever. They have managed to become multi-millionaires however.