//NJ the lines we already have could be upgraded. No need to despoil other areas.//
No they cannot, Lady J. The East Coast and West Coast main lines are running (in normal times) at their total capacity for much of the day. There are no more "paths" available and trains are running at their minimum headways most of the time. The WCML (which HS2 will mainly supplement) has gone through two periods of major upgrading in the last sixty years. Both lasted over a decade, were enormously expensive and tremendously disruptive - and they have maximised capacity as far as was practically possible. Trains run over those routes at 100mph plus at five minute intervals (the maximum that can be achieved safely) and the express trains have to be interwoven with local and freight services. There is simply no more "upgrading" that can be done. You need to read up on railway technology and development, Lady J (which I have been doing for much of my life).