Trains in the Glasgow area run as driver-only, but should have a ticket inspector on board. I'm going purely from memory here, but they wanted the new E&G trains to run on a similar basis, and there was a bit of a stooshie. The result was that the new trains will be driver open, guard close. I can't speak for Wales.
That's my understanding too.
There's no reason why DOO has to mean "no Guard on board" - it only refers to "operation" - i.e. who is controlling things - the driver can press a button to open doors when the train arrives at a station and close them when the train is ready to leave regardless of whether there is a second crew member on board.
The Unions are obviously happy for passengers to believe that "DOO" means the same as "no Guard" (rather than the reality of "there'll be a Guard, but they won't be responsible for safety critical things like operating the doors).
The problem is that we seem to get into a position that is agreed but operational reasons mean the goalposts move - e.g. it was apparently fine for DOO on Glasgow - Drumgelloch and Guard operation on Bathgate - Edinburgh, but then the line between Drumgelloch and Bathgate opened and both sides saw an opportunity to force their favoured situation on the other half of the line... there's been no Guards required on London - Oxford trains for some time IIRC but now the Unions are using the introduction of 800/801s as justification to go back to having a safety critical guard on every service... meanwhile all new trains are built with an eye on the future so have settings capable of permitting DOO but that doesn't mean removing the Guards - however Unions obviously get nervous about the new trains having that capability even if the TOC isn't trying to remove the Guard responsibilities).
Maybe we'll have the same argument soon at Rotherham (local trains require Guards to operate the doors, but the Supertram extension will see tram drivers pushing all of the buttons, so Rotherham station will see half of its service run by DOO trams). Great...