I'm in the no camp, and I live no where near the proposed HS2 route ....
Just looking at the ECML for example, there is a number of things that can be done to increase capacity and reduce journey times.
- Quadruple Welwyn (It will be expensive, but I believe it is being considered).
- Hitchin flyover (already under construction?)
- Quadruple the route all the way between Kings Cross and York
- New 125mph alignment from Northallerton - Birtley (just south of Newcastle). Cut out the tight, twisty and slow section of the ECML around Durham and Darlington.
- A new 125mph alignment between Newcastle and Edinburgh. It's currently 121 miles by rail and includes quite a few slow and twisty sections, plus goes the long way round. By road, it's 105 miles*
On the WCML you could have all trains run (semi) fast between Euston and Watford Junction, with a 10 minute frequency on the DC serving the stations between them. That would free up paths and add capacity on the Southern end of the WCML.
On the GWML, I'm sure there's room somewhere to build a new 125mph alignment between Exeter and Plymouth ....
*Distances measured from Newcastle Central to Edinburgh Waverley. it's 105 miles going via the A68 and A696 or 122 miles going via the A1.