Has it ever been calculated how much it would cost and what would be involved to convert some section of the network to a full continental loading gauge?
I know loading gauges have been increased for larger freight containers, so the methodology must exist.
I'm just wondering if anyone has run the figures/done the relevant design costings for it.
One of the big problems is that there would be even more accessibility problems, even with the "high platform" version of continental standards, for existing stock. And the continental (I'd go with GC+, giving more space than on eg most French double deck lines) stock would be captive.
Ideally you'd convert a whole line in one go. Spend a couple of years doing structure works (tunnels will be a massive pain). Convert platforms but then add a temporary structure bringing them back to current GB standard- this was done at Stratford International for the Olympics on the International platforms to allow them to be used by Javelins. Build a whole new train fleet. Get it tested and fully run in, and send drivers (and guards, preferably) on a "holiday" to train up. Build new depots on new sites and have the new stock delivered there (by road).
Then, in a single blockade, remove all the platform extensions and introduce the entire new fleet in one go. Good luck!
Now, the big problem is interoperability. On our network lines are not that separate. Even C2C run service into Liverpool Street via Stratford. If you had a plan to do the whole country in stages you could consider "interface" stations with platforms at both positions. "classic" stock could run through "new" platforms obviously- so you could say do all the London commuter lines first and retain "intercity" platforms at the terminals.