HH-53 "Jolly Green Giant" Sikorsky Helicopter

Can anyone please help me?

I have seen a few of these flying over my village near Ware, Hertfordshire lately, low and in ones and two’s.

I have done a google to see if any of these are based in the UK and I cannot find any. There are references to Mildenhall but how old these are I don’t know.

Are these on attachment to any USAF or RAF stations at the moment?

Thanks.

B.P.