I  wish to do the NYB or the LPC in London.I have completed my LLB but not sure which is the best course and where to do the NYB in London? 

You actually have to travel to NY to "sit" the exam, although Holborn college offer a distance learning course which lasts a few months. I did the CAL bar via self study and just purchased the books from BarBri online - about $900 for the full set.

Having said that, any US bar qualification will be useless to anyone without a full US JD, at least for jobs in London. UK firms hire only US JD grads from the top 20 US law schools to do US law (usually securities) in London. That NY Bar qual on your CV won't help you land a job over even an equally qualified candidate without it.