Kripes! We are on the island of Great Britain!
France is on the continent of Europe. It is more than 2.5 times the physical size of GB and is directly connected to Spain and Germany, which are all roughly the same in size, as well as Italy at 1.5 times the size of GB. All of their high speed railways are inter-connected. If Paris is the hub the relative capitals are all about 1,000km away. They are all on one land mass and in the same trading bloc. It is not that difficult to make out a case for them to be connected with high speed rail.
By the time we get HS2 we will be almost half a century behind. Maybe it would be better for us to look at alternatives. Decent speeds on comfortable trains connected and running to all parts N.S. E. and W. would be a good start.