" I suspect that any legislation will be along the lines of:"
The legislation already exists. It's called RIPA. However it needs a "Technical Capability Notice" to be approved by Parliament. As described here The text of the draft is here
IOW a form of "Statutory Instrument," much beloved tool of the Dark Lord Mandelscum.
Note. Both house of Parliament have to approve it. Since it requires critical thinking skills (not something you see a lot of in politicians) to realize what errant BS.