The current discussion of this started with #1546 where I merely said there had been talk of it being slowed down, not scrapped. However, in three months we've had three prime ministers and a huge financial crisis, with lots of policy reversals and speculation in all directions, which only reduced a bit a week ago with the autumn statement. See for example
this thread.
To summarize what I think is the current position:
Ministers have committed to HS2 reaching Manchester.
Phases 1 and 2a have Royal Assent and HMG go-ahead, and a confirmed funding envelope.
However major contracts are not yet let for 2a, so it will be some time before we reach the "point of no return" that we have on Phase 1, with contracts let and costs pretty much settled.
The Bill for Phase 2b West is still in its early stages of going through parliament, and is subject to alteration until that concludes, sometime in 2023/24.
And there's always the cost issue - the worst thing that could happen is if Phase 1 or 2a goes heavily over budget.
Remember the IRP £96 billion includes the cost of HS2 completion as well as NPR and other projects in the plan.
Well the maths around OLE and high speed is fairly well understood by both engineering firms and university departments in the UK as well as in France. The UK has it's own 300kph line, remember and 300 to 320kph isn't the same leap that 320 to 400kph would be. I suspect that whoever the design consultants are will be asking the French, Germans and others about it though just because it's good to hear lots of ideas.
For what it's worth, HS1, including its electrification, was a French/SNCF LGV clone.
Some of the contractors for the recently-built French LGV 320km/h ETCS lines are already involved in building HS2 (eg Eiffage - as in EFKB JV).