More or less my exact thoughts. It's just short-sighted to put it off any longer. We need new rail infrastructure; there's not much capacity left in the overworked and increasingly expensive existing system. Our loading gauge means that trains can't become wider or taller without altering every bridge and tunnel, they can only get longer.
A new high-speed network can address this. It's a clean sheet and can be designed for the future needs, we rarely get a chance to do this.
As for alternatives? Bigger airports and wider motorways would surely aggravate NIMBYs even more, and still rely heavily on oil.