It looks like all his companies in Finchley are at the same address.
Don't bother trying to find "St James's Lettings" at http://www.companieshouse.gov.uk/ - it doesn't exist. Guess what? Company called "Marcus Holdings Limited" (06856276) still exists so all that is a good company if you had problems with Martin Marcus more than 1 year ago. If you had problems with Martin Marcus recently then he might trade as "City Lets (Finchley) Limited" (07447216) - check http://www.companieshouse.gov.uk/ or download certificate of incorporation for free at https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B3gY1hY8GkvyYzllZGYyZGEtZmFkMC00NDllLThlZjktMDIyNzAyZWYyYjlj&hl=en_GB
Feel free to use Money Claim Online at https://www.moneyclaim.gov.uk/web/mcol/welcome
Many people (more than 100 now) are contacting me about problems they have with getting money back from Martin Marcus. I strongly advise you to ready my blog to avoid problems. If it's too late then don't hesitate to contact me at citylivinghackney@googlemail.com and report your problem to the Police and Trading Standards.
Guess what people, Mr kash and martin marcus came round to rent my property together...kash arrived first and said his "boss" was just parking......just a pair of bullshitters