The first thing to do is to inform your bankers about stopping all payments out of your account.This includes electronic transfers. Second is to withdraw all monies from your bank so that no large value transaction can be done. Lastly, inform the London company saying that you are refusing all requests for payments of any kind without any form of local due diligence and reporting the matter to the Interpol or the British Police as well as the local Indian police. These measures will scare away the scamsters till they find a new scheme to lure you into it.