ElBogster,
Re: Euston - The current trade off on many routes from BHX is - shall I use my local, more expensive airport or go down to London for higher frequency. Often the local airport wins, especially as higher fare is offset by not paying for petrol / fare to get to a London airport.
Do this in reverse - shall I ignore all of London's (9 by then?) airports and go out to the sticks to use a more expensive, less frequent service, not to mention an extortionate rail fare on top?
Re: LHR - my understanding is there will be a stop at Old Oak Cmm / Wormwood Scrubs for tfer onto Crossrail - or a facility out by the M25.
I just don't think HS Rail can work to regional airports - my suspicion is that we will end up with a white elephant like Lyon Satolas, except we won't get the impressive architecture that goes with it