I am now being hired by someone in London and he told me to send an email to the travel agency , is this okay?

Visas are granted by the British government, not some random private agency. Do NOT give these people money. There are many, many immigration scams, and this reeks of one. Consult your local British embassy or consulate to check on the validity of this organization. Chances are they're full of it - as is the job offer, if they insist you go through these people.