Gr4, hydrant refuelling has had a dismal history in the RAF. All V-bomber bases were so equipped but there were problems. One I heard was contamination, they might have been left empty too long or there was a pressure problem.
Brize had a fuel pipe network but when the USAF pulled out it was abandoned only to become a massive environmental problem years later.
The other problem in the cold war was lack of resilliance and flexibility. Disrupt the network and without bowsers you were fooked. I don't know about HAS sites.