Mike,
I've been working on a map showing the status of the electrification on the GWML posting over at Railforums using the same username for some time now, however, I've had to take a break from doing it for the last couple of weeks, but I hope to re-start work around mid-May.
Right now it covers Maidenhead-Swindon, minus the B&H further than Reading West and the line to Oxford further north of Appleford.
If you, or other members of the forum would like, I could try to rush a 'half finished' version out showing the status at some point today.