So a new line to Heathrow for their benefit etc, unlikely to be paid by Heathrow but taxpayers, reduced rail service to London from Slough to make room plus timetable changes - now we know that will be fun.
Where did you get
unlikely to be paid by Heathrow
from?
To be fair Heathrow's owners have been messed about considerably with the whole third runway fiasco and have had to foot the bill for all the delays and redesign works. After what happened with the Crossrail link I would be cautious in making concrete promises too.
The Western rail link has an outline design but once it goes out to tender this design will be improved and pulled apart by the various contractors and the final layout will likely be different to what they have now.That being said they would be crazy to come out and say there will be no delays. One of the high scoring items by the winning bidder will be how they mitigate the disruption to existing services but at some point there will be a connection made or heavy plant used near the line that requires temporary closures.
Crossrail will take much of the strain off of the existing GWR line so the capacity that will be available then is not necessarily available now.
There is no doubt that, third runway or not, a rail link out west without the need to change at Hayes is needed and long overdue.