Update Dec 17 Two weeks ago, BT was fighting back against the Huawei boycott. The Security Forces have since grown stronger. The cost to Britain will be in the US$billions.
The U.S. security agencies are currently pressing England and Germany to cut off Huawei, which everyone in the industry believes would be a very expensive move. BT is smart enough not to take on MI5 and GCHQ directly, but would have to spend many billions more if it lost Huawei and ZTE as suppliers. Update 11/28 New Zealand, one of the Five Eyes working together since World War II, has now cut Huawei out of the 5G plans.
"There is only one true 5G supplier right now and that is Huawei -- the others need to catch up," says BT Chief Architect Neil McRae. That comment makes it easy to draw the inference that cutting off Huawei would significantly slow down England's 5G deployment. Even if BT says nothing, others can and probably will assert that it would be a mistake for England to boycott the Chinese.