The great irony is that the fast charge trial with 230001 is going very well. Everybody and their dog has been to see it, pose next to it, use it in their presentations as the poster boy of rail decarbonisation in the UK. The DfT themselves speak highly of it. But the sad thing is that with all the uncertainty in the rail industry at the moment, budgets under intense pressure, and with GWR to be consumed under GBR within the not too distant future, no decisions are being made. About anything. So I can see the whole thing just fading away, not because it's technically difficult, but because of a lack of decision making. I think the GWR fast charge trial will end up being one of those 'flash in a pan' things, a nice end to the troubled Vivarail legacy but didn't really go anywhere because of political stasis. I may be wrong, but that's how things are looking at the moment.
With regards the ex-WMT 230s, they were at Reading until quite recently, but they were moved out because of the impending HS2 diversion works at Old Oak Common, meaning that space for stabling / servicing other units at Reading is going to be at a premium. The gensets are similar to those used on TfW, but TfW have since undertaken so many mods on their gensets that they wouldn't be directly interchangeable. However, the parts within the ex-WMT gensets would have been useful as spares to TfW. You're quite right about the difference in power architecture between the WMT and the TfW units.