The National Cyber Security Service are actively scanning UK servers for vulnerabilities. If you own a server you can check in your logs to see if you have had a visit from 18.171.7.246 or 35.177.10.231. This relatively benign oversight is being done to build up a view of how vulnerable the UK is to a cyber attack. Its better than nothing but all it will do at the moment is to alert you if your server software is out of date or vulnerable.
The details of what is being done and why are given in this link.
Unfortunately this will not protect us against the Stexnet type attacks carried out by the US on Iran. The weak link in those cases is people, and unsafe/unthinking actions.
As I said, the NCSC action is better than nothing, but really a higher degree of Sysadmin alertness in locking down systems might be a better measure.