Summer job in Creative Marketing ltd, add. 32a-37 Cowper Street Old StreetLondonEC2A 4AW0207 336 665?

I just called the phone number and it's invalid, and also cannot find them when searching Google. So my first thoughts would be that they don't exist.

However, it is possible that perhaps you've taken the details down wrong ... there are many small marketing companies who would be looking to take students on for the summer to do crappy jobs like cold calling and approaching people on the street, so it's likely that it could be one of these types of places, and they may be so small that they don't even have a website.