Banning Huawei makes UK networks more vulnerable and more expensive
Any provider worth it's salt would build at least two different vendors across it's core - e.g. Cisco and Huawei. This is so that any bug that hits a single vendor only effects half of the network. If it's built right that would only result in a lack of resilience rather than an impact on service.
So what Trump's done is he's blocked the export licences of various encryption standards owned by US companies to China. Rather than write their own Huawei just bought them in under licence. Without this licencing agreement in place they cannot run encryption standards that allow them to interface with other vendors. It's not that Huawei are using some kind of Chinese spy code - they are using code written by and patented by US companies. Now Trump's stopped that.
So the result is we just have one US vendor who can charge what they like and absolutely no resilience against bugs. There is no increase in security since as before they are running US written encryption standard code - if it's got a back door it'll be to the NSA not Beijing. Some minion in GCHQ has obviously been asked to brief the Govt on the impact of Trump's ban and the answer has been - well you can't have Huawei in the network running unlicensed software and this has been spun into some kind of security vulnerability. It beggars belief.
All because Trump screwed up big time and needs to blame China for corona-virus in an election year. And all because Boris is a spineless oaf desperate for Trump to win a second term and bale him out with tins of chlorinated chicken when his no deal Brexit hits the fan in January.