An article in the London Evening Standard suggests that many Magic Circle firms have already sent legal work to India and South Africa (e.g. Allen & Overy, Clifford Chance, Eversheds, Lovells and Simmons & Simmons.) The article reports that 1000 more legal jobs may be sent to India by the end of the year.
While the article does not provide a lot of concrete evidence that this is actually occurring (it mainly quotes various individuals in the legal and LPO industries), I am left with the impression that the U.K. is taking more quickly to outsourcing legal work to India. I cannot recall seeing an article which lists as many American law firms adopting the practice.
If it is really the case that U.K. firms are taking more quickly to offshoring legal work, perhaps this is because of the strong colonial history between England and India. There is a large population of Indian immigrants in the U.K., particularly in London, and I suspect that your average English solicitor or barrister has more contact with professional Indians than you average American lawyer.