Indeed, 158766.
As for the other two 2-car 158s, 158951 is working the 3-car 158 diagram that goes to Brighton, starting with the 0723 Warminster to Great Malvern, 1050 Great Malvern to Brighton, etc
158763 is working the 3-car 158 diagram that starts with the 0749 Bristol Temple Meads to Weston-super-Mare, 0841 Weston-super-Mare to Cardiff, 1100 Cardiff Central to Taunton, etc.
So for anyone who's interested, here are the diagrams for the 2-car 158s today:
158763:
2Y05 0749 Bristol Temple Meads to Weston-super-Mare
2U08 0841 Weston-super-Mare to Cardiff
2C73 1100 Cardiff to Taunton
2U18 1307 Taunton to Cardiff
2C83 1600 Cardiff to Taunton
2U28 1808 Taunton to Cardiff
2C34 2100 Cardiff to Westbury
158766:
2M02 0517 Gloucester to Southampton
2M97 0823 Southampton to Great Malvern
2O90 1250 Great Malvern to Weymouth
2V93 1730 Weymouth to Bristol
(as posted by trolleyman)
158950:
2G80 0715 Gloucester to Great Malvern
2F97 0850 Great Malvern to Westbury
2D17 1438 Westbury to Bath Spa
2R98 1553 Bristol Parkway to Bath Spa
2D24 1643 Bath Spa to Bristol Parkway
2C22 1748 Bristol Parkway to Westbury
2M17 1932 Westbury to Cheltenham
(so diagram 2 as posted by northernrailer)
158951:
2E17 0723 Warminster to Great Malvern
1O98 1050 Great Malvern to Brighton
1V96 1659 Brighton to Bristol Temple Meads
You've missed out something.
The 1438 from Westbury goes on from Bath to Bristol Parkway, then it works 2R98 1553 back to Bath, and then what you've got to Westbury on the 1643 to Bristol Parkway and 1748 return to Westbury, then it works the 1932 to Cheltenham.
So it's as follows:
2G80 0715 Gloucester to Great Malvern
2F97 0850 Great Malvern to Westbury
2D17 1438 Westbury to Bath Spa
2R98 1553 Bristol Parkway to Bath Spa
2D24 1643 Bath Spa to Bristol Parkway
2C22 1748 Bristol Parkway to Westbury
2M17 1932 Westbury to Cheltenham