They didn't seem familar to me as a UK company
"On 10 February 2011, Dialog semiconductor announced that it had completed a transaction to acquire SiTel Semiconductor"
They indeed are not very British
Dialog Semiconductor originated from the European operations of International Microelectronic Products, Inc. – a Silicon Valley company founded in 1981. Then 1989 Dialog Semiconductor formed as part of Messerschmitt-Bölkow-Blohm (part of Daimler-Benz).
According to Wikipedia, which doesn't entirely make sense.
September 2009 – Relocates to new Swindon facility (from Germany?), hence the "UK" connection.
December 2012 – New Design Centers in Livorno, Italy and Istanbul, Turkey
July 2013 – Acquires iWatt Inc.
They seem to have an Edinburgh centre since 2007.
I guess the Ardunio folks will be nervous for a while.