Freight can be transported overnight.there are regular night/early morning trains from the Milford Haven refinery. Also, coal used to be transported out of hours on the main lines. In ours teelworks we had a bulk transporting by rail to a mill in The Midlands. Passenger traffic is for daytime requirements with limited needfor nighttime.
The tracks are under used at night.
There is already a basic rail network and so the infratructure would need tweaking to distribution centres sited with logical location to marry with ports, roads.
Not such a big cost as a complete overhaul which would be unnecessary. Yes there is a need to modernise signalling and maintain tracks but that is needed anyway not just to create freight requirements.
The HS2 funding is likely to have been sourced already, three sources would have been EU, Private sources and taxation. EU moneywill disappear so how would HS2 be funded?Maybe the EU will honour commitments made as the UK has said it would to similar circumstances. Will the interested private parties cough up? After all, if the economics of HS2 are so attractive then why not? Taxation? Yes a thorny one. Fares will have to be inflated to cover the cost to reduce the tax bill. You want 10 mins off your time of trave? Then pay for it!
It all adds up to a project crying out to be cancelled.
