RAF Fylingdales (and I guess the other base he mentioned) is home to US-UK joint nuclear missile warning systems. In this case (radars) having a forward radar in Europe/UK is beneficial to US nuclear defense.
Logically, you can make an argument that warning satellites such as DSP (hyuck hyuck hyuck) and SBIRS would cover that, and they do (and a far better job since I believe radars can only reach out so far unlike satellites, and satellites pretty much watch everything all at once) but having a multi-pronged approach to a solution helps just for redundancy since warfare, including nuclear warfare is a game of 5D chess.