There is no London Marketing Services at 14-20 Shand Street. The only businesses with registered addresses there are:
Cameron Taylor Brady,Shand House 14-20,Shand Street,London, SE1 2ES
Clarke Bond Group,Shand House 14-20,Shand Street,London, SE1 2ES
Komex Clarke Bond,Shand House 14-20,Shand Street,London, SE1 2ES
There is also no company called London Marketing Services registered with Companies House, which is the national registry of all registered companies in the UK
I suspect you are being scammed. Cut off all contact with these people.
Have you even interviewed with one of the companies listed above? If not, there is no job. A recruitment agency cannot hire you for a job. All they can do is introduce you to potential employees - but then you have to interview directly with the employer who would be the one to hire you. A recruitment agency cannot give you a job offer or sponsor you for a visa - only the actual employer can do that.
So unless you have had an in-person interview with either Cameron Taylor Brady, Clarke Bond Group or Komex Clarke Bond, there is no job offer and you are being scammed