FTA: "This includes 400 staff at Dixons’ Hemel Hempstead-based HQ that did not want to relocate to Carphone’s equivalent office in Acton, a driving distance of a little over 25 miles."
It might be "only" 25 miles, but have you tried to drive south from Hemel to Central London in the morning? It isn't going to be a 20 min pop down the M1 at 70 mph that's for sure!
FTA: "One insider told us the costs of revamping the dusty old Hemel building was considered too high, and Acton has a larger footfall so has more room for expansion."
I thought the Hemel building was badly damaged by the Buncefield explosion in 2005? Anyway I would expect a building in Hemel to be cheaper than one in Acton.
Also "larger footfall" doesn't imply more space for expansion.