With regards to this, will there be an Up Westbury to Down Westbury crossover south of Reading West, for trains to run through the Down Westbury Platform at Reading West? Or is the Down Westbury being made bi-directional for reversals from the Down Westbury Platform?

If that makes any sense.

In answer to your question johngreg, I believe the only visual differences will be some of the signage. The on station staff are all likely to remain FGW^▸ (First Great Western), but the "behind the scenes" stuff is to be run by Network Rail.

At least that's what I gleaned from the radio.