Think about it Dan, the HS2 is going via Birmingham, and won't be doing 225mph all the way, there will be times when it slows a bit, for a bend for example, and for the station stops in the middle of nowhere. 225 mph is the maximum speed not the average. Some present trains are capable of 140 mph but rarely go over 125 mph, and average around 100 mph.
Not going to happen.
The route from London to Manchester won't go via Birmingham although there will be Manchester - Birmingham trains and London - Birmingham trains.
The route will be much straighter than the existing route and so slowing down for bends will be less of a problem than it is on the existing WCML where tilting is required on stretches.
The existing Pendelino fleet are rated at 140mph but are limited to 125mph because that is the line speed of the route. The last major upgrade should have increased the line speed but it proved too costly.
Hope that clarifies a few things.
Gavin.