Concerns about the influx of US-owned design businesses into the UK are unfounded. The presence of US firms in the UK has helped raised the quality of work being created. It should be seen as a boon, not a nuisance.
US design companies have generally been more sophisticated than their British counterparts for a number of reasons. Those on the West Coast were close to developments in Silicon Valley, and many of the movers of the Internet economy were their long time clients. Also many of the global corporations that made the first commercial moves on the Internet have US headquarters and looked to US design companies for assistance.
Hence these companies arrive in the UK with valuable experience from which the design community here can greatly benefit.